Ok, I guess I misinterpreted your post. But I'm not sure if you even read my entire post; MK flying is overestimated as really fast; as long as Kirby can squeeze in even one slide attack, and continuously run/jump nonstop, then it is not faster for Kirby to get on MK's back, for horizontal sections (and there are far more horizontal areas than vertical/diagonal). Heck, even if Kirby can just run/jump without stopping/puffing in one screen (very doable, cuz this is kinda TAS) it's faster to not use the partner at all because it takes time for Kirby to get on MK's back.
The reason why I say co-op won't be overall that useful in a speedrun is because more than half the time of other players is spent just trying to keep up with Kirby (who better have some mobile ability) and falling behind. There are obviously niche spots where a second player can come in handy (aka hitting a switch and entering a door simultaneously, or getting an energy sphere). But for the most part, it's not only because of damage scaling; damage really doesn't matter if Wing/Fire/Water/Tornado Kirby can just plow through everything far ahead of the other players.
The fact that you say Fire is faster shows that you really haven't played with Wing enough. Wing >>>>>> Fire by a longshot. Fire may give a little more distance per burning than per condor head, but...
-Wing maintains height MUCH better (aka you don't have to land and readjust height), and it might be able to maintain height perfectly with frame-perfect condor heads
-Slays bosses generally faster than fire
-jump-canceled-dive-door-entries
-Flies vertically+diagonally better (yeah, it's better to use Wing Kirby than MK since Kirby won't have to get on MK's back)
-dives are ridiculously fast for downward movement and kills everything via combo dive / dive bomb; it's only bested in downward speed by stone (barely), sword, and maybe spear (where sword and spear's down attacks don't even have invincibility in the duration of falling)
-has much more invincibility than fire, and so on.
Add in the fact that Kirby can Combo Dive / Dive Bomb any time during Condor Heads, and jump-cancel during any of these dives, and there is so much more versatility in movement. And since this is TAS, given how technical Wing is, using Wing will save so much more time than using fire. And I'm still confident that Wing is still horizontally faster than Fire, because burning has more startup+endlag than condor head (which has practically ZERO startup and minimal endlag, but you can cancel condor head any time with a dive bomb / combo dive).
You should check this out for actual damage data
http://www.gamefaqs.com/boards/935607-kirbys-return-to-dream-land/62398037
And also my any% current record
http://www.youtube.com/watch?v=ecLncXnHPN4
Some things I can easily point that that you can only do with wing and not fire
0313 - The first of many jump-canceled-dive-door-entries, which saves time (and by TAS, you can do this with basically ANY DOOR), because you dive down so fast towards a door and enter it instantly. This also applies for goal doors.
0357 - Combo Dive at the end of Condor Head gives Kirby a block of height, and maintains most of his speed. You really don't have that degree of control with Fire, even in TAS.
1031 - Another jump-canceled-dive-door-entry, and also how shockwaves from dives can destroy bomb blocks very conveniently without slowing down. Fire has to come all the way to the ground and use burning to plow through the bomb block. This also applies for switches on the ground. In particular, if you have to wait for something to happen after hitting a switch/bomb, obviously you want to hit it ASAP; wing can activate switches more quickly and from farther away thanks to shockwaves.
1133 - Wing can kill this Bonkers before he does his time-consuming spin attack. Fire can't. Nuff said. There's also a Moundo in 3-3 that Wing can kill before Moundo does his even-more-time-consuming spin attack, but I didn't get it in my any% run (I got it consistently nowadays though). Fire can't do that. In other words, Wing destroys every miniboss much faster than Fire can (besides 1-2 gigant edge and 2-3 king doo, solely because inferno can finish them before they attack; this doesn't work later on since they have more health)
1720 - Try navigating this room with fire. I mess up a bit, but I'm sure that my any% performance in this room will be faster than TASing it with fire.
2103 - One of a few noticeable spots where descending with wing is ridiculously fast.
11140 and 11202 - Examples of Combo Dive being amazing, whereas fire has nothing of the sort
Furthermore, distance of burning may be barely greater than Condor Head, but Condor Head + Combo Dive has farther distance with invincibility than a single burning; this is significant as it allows Wing Kirby to condor head + combo dive through obstacles with more versatility (aka huge boulders, monster-fire obstacles, etc). This is more of a console safety thing though; not sure if it 100% applies for TAS since you can probably do pixel-perfect burning/condor heads to get through obstacles anyways.
The camera quality of my run is absolute crap, but you better watch my entire any% run to see how wing is so much better than fire, and it's probably even better TAS, given how technical it is. I'm almost positive that any% sub-140 is possible on console, and definitely on TAS.
I really do want to see a 2-player co-op TAS. For 100% though, I better see Kirby getting wing at almost every possible opportunity, or else the run is automatically sub-optimal. Also, it seems like you really haven't messed with wing much in general. Wing is undoubtedly the best overall ability in the game, but also the most technical (which is overcome by TAS). It is the most mobile, with the most invincibility, and one of the best three abilities to speedrun bosses with (other two are hammer/ninja, but neither have close to the mobility that wing has).
But for 100%, Fire is still one of the more mobile abilities. Fire Spin is great for vertical movement, and remember that you can do multiple consecutive fire spins along walls. I seriously suggest you watch both my any% run and yoshifan's 100% run for a route to base things off of.
Also @CoolKirby, I may take you up on your offer about TASing in general, since if I'm ever to learn TASing, it'd definitely be this game, but not for now. I'm still speedrunning KRtDL and KSSU on console D
EDIT You're also wrong about DDD being stronger than MK; MK is actually stronger than DDD, and DDD does considerably less damage than Hammer Kirby with everything; for example, DDD's hammer flip only does 45 damage whereas Hammer Kirby does 80. (68 and 99 respectively if reversed). The only advantage DDD has over Kirby/MK/Waddle Dee is that he is a tank, and has considerably more HP (and MK has the least HP, and Kirby/Waddle Dee have equal I think).