What the heck does fair have to do with anything?
The difference is Hendricks is only slightly "bigger" than GSP but regularly fights at WW. Silva is noticably bigger than GSP and regularly fights at MW.
If GSP fights Silva they'll both weigh-in exactly the same the day before the fight.
By fight time, Silva would likely have a 15-20 lbs advantage over GSP.
It's neither fair nor unfair; it's simply reality. Size matters. That's why there is weight classes.
Silva's height and reach would be much bigger problems for GSP to solve than whatever weight Anderson walks into the octagon at.
According to stats. Anderson holds a 2.5 or 3 inch reach advantage.
I am no expert. But if they met at 178 Anderson would be around 200 on fight night and GSP would be his usual 190-193.
Height may play a factor. Carlos Condit is 6'2 as well.
In any superfight someone is going to be at a size disadvantage. Fact is Anderson doesn't really use strength or size to beat anyone. He uses accuracy, footwork, and technical skills.
People seem to want to talk about Anderson's advantages. Lets actually talke about GSP's big advantage.
GSP cuts a lot of weight to make 170. If he had to only go to 178 he would hold more strength than usual and would not have to try so hard to make weight. That process would be a breeze compared to his usual routine.
Anderson at 178 would come in drained. Imagine if GSP came in at 164? You don't tthink that would take something out of him? Anderson will have less strength than he has at 185.
So in the realm of things GSP holds advantages in a catchweight fight. Do we think Anderson would have stayed as fresh and have enough energy to finish Chael if he had to cut 7 more lbs for that fight. I would say no.