Why I think board height doesn’t matter (in absolute terms – i.e., efficiency, acceleration etc) and if it did, lower would be better.

The “top mount offers more leverage over the trucks” argument is void.

The rider on a dropped deck is closer to the pivot axis of each truck. Therefore, the lever is shorter.

The lever to do what exactly? To turn the trucks.

And how do trucks resist turning? With bushings (or springs, or TT’s arms).

What do we do when they resist too much/little? We change them.

The end.

(It is true that the difference in leverage between a dropped and a top mount deck might be too small for the rider to bother to change bushings when using the same trucks on the same angles. Therefore, to that rider, it would indeed – accurately – feel like that a topmount offers more leverage over the trucks and better acceleration. Later the rider might change bushings, but cause-effect link is lost.)

(Another way to gain more leverage over your trucks is to use a wider deck. Would we also say “wider decks accelerate faster”? Well, we could, actually, but we don’t.)

Why it’s possible (but not certain) that dropped decks are more energy-efficient.

I haven’t researched the following enough to say conclusively, but it seems like there’s energy advantages to a dropped deck. The argument is as follows.

On a dropped deck, the center of gravity of the rider moves less laterally and vertically in relation to the deck than on a topmount (all other things being equal).

Image to illustrate (top curve is for a topmount, bottom is for a dropped deck – random numbers, only to illustrate the point):

It’s possible that the lateral movement does not matter, because the board also moves laterally (i.e., the pumping motion), so I’m provisionally going to concede that the extra lateral motion of the topmount is part of (but differently timed than) the pump itself. In other words, this lateral motion is absorbed by the lateral motion of the pump. On the dropped deck it happens as well, just on a different kind of frequency.

But what about the vertical movement? Clearly, on a topmount there’s more of that vertical up-down. But this one it’s not absorbed by the pumping motion. It’s still there and it’s bigger on the topmount, smaller on the dropped deck.

And here’s the obscure bit: is there energy lost due to that extra vertical motion? I’d say yes. The bushings burn more of their PU molecule links (or whatever), or the springs wear out faster, and/or the rider’s muscles make more effort to lift their body back up and towards the middle of the pump.

The end? No, there’s a counter-argument. One could say that the vertical movement is actually also part of the pump, since the rider uses their gravity vertically to facilitate the pump. I wouldn’t be able to respond to that. Perhaps this paper might help this debate. Kook55 from Pavedwave also made a compelling case why the vertical motion is not only integral to pumping, but also that the more there is, the better.

“It seems roughly analogous to the same physics of a kid riding in a swing: the kid has to swing his (or her) legs pretty hard at first to get going, to get higher, weighting down as the swing drops, swinging legs up at the bottom and reaching on the way up, then unweighting as the swing starts to fall back. But once the swing is going, past the early stage, it takes less and less energy to add to the swinging and rise (until it reaches a point of diminishing returns closer to the vertical). That’s what it feels like, pumping the right set-up, that middle part, when it’s easy to add to it, just weighting and unweighting a little bit. I guess physically, you could say that potential energy, in the form of gravity is “stored” in the system of the kid on the swing once it reaches a certain point, energy that was built by the progressive addition of verticality. In a similar way, the momentum of a skater and deck builds, (horizontally, a body in motion tends to stay in motion, etc.) and can be added to with the right set-up in a way that utilizes flex and weighting and unweighting. Doesn’t work with decks that are too stiff, too short, anything off and it doesn’t click. […]
The swing analogy was the best way that I could come up with to visualize and describe what it feels like. In action, it is both up and down, and left-right. I actually visualize it like bouncing off two little trampolines at a certain point after the mid point of a carving turn – with the trampolines angled at 45 degrees and slightly forward. That’s what it feels like. (I was originally going to draw a diagram to illustrate this before you raised this point.) I don’t think that this is fundamentally necessary to the process of pumping (I just don’t know, I haven’t thought about that point), but I think that vertical forces, combined with the flex and the other elements of this type of set-up, clearly add to the dynamic energy of the pump.”
(Kook55)

In conclusion: vertical movement is in principle unnecessary (albeit probably helpful) to do slaloming. “Everything should be made as simple as possible, but not simpler,” so I would recommend moderating our expectations regarding board height.

What do I think about arguments not claiming in absolute terms one is better than the other?

Dropped decks are less strenuous when pushing.

Yes, obviously. But, James Peters disagrees:

“I don’t find topmount to be more strenuous to push than a dropped deck. That might be because I’ve always stuck to some principles: – use wheels no larger than 75mm – use only required amount of riser, such that wheel comes close to deck without touching – carve wheel wells into the underside of deck (best to make this the design of the board / either sawing by hand or CNC process) – keep the ground to top of deck, total height, under 5 inches – use a deck with at least some minimal flex – (technique) expect to push using the toes and ball of foot, not the full foot, unless pushing up hills – (technique) expect to bend the knee when pushing uphill, which is a natural motion. Shouldn’t need to bend knee much at all if using toes when pushing flats. Many people set up their topmounts with a lot of riser, to accommodate bigger wheels. The main reason I still ride topmount is 1) more fun to pump (subjective) 2) I feel safer at speeds of 30–40mph on topmount, maybe because of past experience in slalom, which also made me learn how to foot brake really well at speed. I believe the skateboard industry shot itself in the foot by promoting the idea that dropped decks are “so much easier” to push. I understand wanting to sell more boards, but I wish they had been a little less discouraging to people who preferred the feel and ride of a topmount. Some people simply don’t like the dropped deck feel or they don’t like the possibility of hitting a wheel with their foot and wiping out, or actually do that and wipe out. Then if they want to get a topmount after all, now they have this false idea planted in their heads that “topmount will be a huge sacrifice in comfort” which is BS. And now they’ll start looking at Razor scooters or ONDO boards or roller blades or crystal meth or sell themselves for sex – thanks a lot skateboard industry! I understand how too many people based their initial experiences on poorly set up skyscraper topmounts and were discouraged. I didn’t use to really care about this, until I started seeing some board makers or older dudes claiming that people were actually “injuring or hurting” themselves just by pushing topmounts … and that really rubbed me wrong. Taking an activity like skateboarding that is first and foremost FUN and good for one’s health, and making it sound like it’s “bad” because they chose a topmount, based on some anecdotal evidence. All that said — I thoroughly enjoy riding dropped decks and own quite a few. And if I were to skate *with a heavy backpack* for weeks at a time, then I would probably choose a dropped deck because the technique of pushing using the full foot to carry a bunch of excess weight is easier. But most of the time I’m not packing all that. Anyway, I know the momentum of the industry and 90% of the skate population will charge forward on dropped decks and that’s totally fine. I just hope board makers keep promoting the topmount as another kickass, fun way to skate and not get too hung up on the ‘efficiency’ — especially when just introducing people to LDP.”
(James Peters)

Dropped decks are less strenuous when pumping.

Well, I think I’m the only one who said that so far, but it feels that way to me. Part of the reason might be what I wrote above about possible energy efficiency. Another reason is, it just feels calmer for prolonged periods to be low and less hectic, to me at least.

Bracket-system decks are heavier.

Not many people say that often, but I guess it’s true in most comparisons. Lighter means you can carry the thing easier.

Bracket-system decks are more expensive.

Yes, mostly.

Topmounts feel better.

That’s subjective, but I agree. I’m still a kid who likes to swing up-down, left-right, and topmounts swing more (see illustration above).

Topmounts look cooler.

Again, a subjective opinion to which I subscribe. They are more of a skateboard (with all the associated history) and less a functional machine.