Yeah, I don't disagree with any of that. I do think that - assuming speed, agility, route running, etc. are the same - the guy who is 5'9" is almost certainly starting behind the 8-ball in comparison to the guy who is 6'1" just because of the laws of physics. The latter guy has a bigger catch radius and can likely high-point/box out better.
In Pitt's case, if indeed we're not able to get the "complete" receivers, or whatever one wants to call the highly-rated guys who have both size and skills, then we had better at least diversify a bit so that we can at least have guys who accommodate certain situations... the red zone not being the least of which.
I do remember Hines Ward being a weapon in the red zone, but a lot of that was contingent on him being built like a LB and having a QB who could fire a 200 mph dart into a tight window while he boxed the DB out. Not sure that's something we should count on at Pitt.