I quit DK for Bowser so I heartily disagree.
Bowser's custom3 down B is much faster, and you can easily head for the ledge with it making it incredibly safe. Mixing up between that, airdodge, and the lower part of fair's hitbox can help you land pretty well.
I wouldn't give up my projectile for Storm Punch.
Kong Cyclone is a good move but kind of cheesy and reliant on ignorance, and it doesn't have the OoS utility of Bowser's Sideb1 and Sideb3. It breaks even at best.
DK's side-b-2 is also a landing option that can snap the ledge, so on Bowser's side is down-b/down-air (basically the same option, down-b is just better; d-air has some use because of the persistent hitbox post-landing), n-air and part of f-air. On DK's side is down-b (this has lag though), d-air, b-air and n-air sometimes, and side-b of his own. If DK isn't taking Storm Punch, then that electrical punch (whatever standard-b 2 is called) charges extremely quickly and can serve as a good landing option. On the other hand, Bowser's side-b dash kl/am is good for avoiding juggles. On thinking about it, landing options are probably pretty even.
Disagree entirely on Kong Cyclone. Relying entirely on it is as your bread-and-butter move is not a reliable way to play the neutral game, I agree, but it punishes airdodges and landings like no other move in the game, and the properties on the move are mathematically better than just about any other move I can think of (speed, distance traveled,
armor: I had a Kong Cyclone eat through Link's d-air with the armor on it and kill Link off the top on Yoshi's). On stages with platforms it also autocancels so punishing it is extremely difficult.
Nothing that Bowser has is really comparable: up-b 3 is hard to punish and can catch some landings, and up-b 1 is a good punish move, but Kong Cyclone imo just flat out annihilates both of these moves head to head.
Bowser's big fireball is pretty mediocre, imo, if that's what you mean by projectile. He loses control over his body for a time while he's firing it; if he could fire it slightly faster or if he didn't lose control, it would be great. Fire breath version 2 recharges too slowly for me to even consider. Fire breath 1 is pretty decent, but there's no way I consider it better than Storm Punch. Storm Punch can completely destroy rolls away and landing attempts when fully or near fully charged. Characters often try to create quick space DK and themselves (because being close to a large/heavy character when you're not in advantage or literally on top of that character in general is pretty dangerous), and Storm Punch capitalizes on that. Combined with DK's b-air and d-air, Storm Punch leads to some sick surprise KOs/gimps.
It's no Tempest, of course (Ike is a beast), but it's better than what Bowser has imo.
Not necessarily saying that DK crushes Bowser or anything, but it's far from one-sided in Bowser's favor. Normals are arguable. I'd take DK's d-tilt, f-tilt, up-tilt, up-air, d-air, and even b-air (in some MUs) over Bowser's equivalent moves, but I'd take Bowser's f-air, jab, f-smash, and b-air (in some other MUs). D-smash and up-smash are arguable.