Honestly, the guys that are ripping winners with a 98" head racquet, would just end up adjusting and rip winners with a 90" head and vice versa. Racquet headsize, weight and string can make some difference, but at the end of the day it is all about technique and consistency. And with this self knowledge, I'm contemplating switching racquets again .
I don't have a stance on this debate but I would disagree with your first sentence. I don't think most would be ripping winners with a smaller head. I'm a 5.0 but probably an extreme case. I've never been a very clean hitter for my level, in part because I hit with more spin than anyone I've ever played. If you have me a 90" racquet, my game would suffer against players my level. On the other hand, I have a 4.5 friend that I regularly beat 2 and 3 but he plays fine with a 90" racquet because he hits fairly flat. I'd guess that most players would play worse with a smaller head. 5" is not insignificant. It doesn't create less mishits but it makes your 50mph forehand 55, and your 25 mph stretch backhand 35 mph. That's where the big difference.