Rather then base my opinion on 20 year old memories I decided to pop Tailspin in today and give it a play through for comparison. Well, I still think Tailspin is the better game even more so then before. With the exception of the annoying delay between landing and when you can jump again in TS, the controls are way way better. Platform jumping and hopping on enemies heads in Darkwing Duck is just a trial in frustration.
Tailspin has different music in each stage versus the same droning theme present in most of DD. Speaking of stages there are 6 in TS not counting the "flying" stage versus 4 in DD. Graphics are about equal, but with more stages TS has more variety.
Again I think both games are pretty mediocre, but Tailspin could have been a decent game if it had a little more polish. On a scale of 1 to 10 I'd give Darkwing Duck a 4 and Tailspin a 5.