I'll see if I can make a test run of a few levels. I played the game to death on the original "super crappy screen" Game Boy and it might be fun...
Edit: According to my testing, jumping and dashing (with just the regular big Wario) seem to be almost exactly equally fast, though dashing seems to be a
tiny bit faster (and by tiny, I mean tiny), but that might just be because of a lack of optimizations on my part. More testing will be needed.
Edit: I tested it once and for all, and I found out that jumping is slightly FASTER than unupgraded dashing. At least it is if Wario bounces off some enemies.
Now to find out which is faster: jet hat jumping, jet hat dashing or dashing with some other hat.
Edit:
Level 1 done quite fast:
http://fast.filespace.org/blublu/blublu_warioland.vbm
It seems like if you bounce on an enemy, it doesn't cause a delay. I also discovered a nice trick; you can pick up an enemy, jump, throw the enemy, and then bounce from it in the air. It looks pretty neat.