The Floatiness is what makes everyone harder to kill. The effect of direction influence is a lot stronger in brawl then melee, so its easier for people to gain momentum back toward stage and thus survive. The Spin attack from melee has lost its good trajectory in brawl and now takes time to reach max power which even then is still weak. But i think the non charged spin attack is about as strong as the melee one with just a more upward trajectory making easier to survive. even with the same trajectory as melee. With the momentum canceling and floatiness of brawl, i think have the cast could still survive it no problem. It would only kill people like Link. But then again people with tether recoveries could just whiplash it to survive.
Frankly i think Link is better in brawl than melee. Just that everyone else was improved more then Link was.
If you look at his move set.
Better: Fsmash, Usmash, Dsmash, Ftilt, Rang, Arrow, Zair, Dair, Bair, Fair
Neutral: Utilt, Bombs, Uair, Nair
Worse: Dtilt, Spin attack, Jab, Aerial Spin Attack
Game Mechanics:
Better: DI, Momentum Canceling, Hit box, Life expectancy (not including gimps),
Neutral: Weight, Jump, Speed
Worse: Recovery, Hit stun
Plus in my opinion the lack of the single air dodge that could be used to wave dash was taken out, making Link more effective at spacing. Instead of having to always be worried about someone sliding right up to ur face with a charged smash.