When a prospect is as coveted as Westmoreland, and has shown the tools he has shown, and the GM of a team who used to work specifically with this farm system asks for him in a trade for a player of A-Gon's caliber, you should re-evaluate the way you're valuing said prospect, which, by the way, seems to be done exclusively on opinion and not stats, following said player, or watching his tools in play. This is a mistake.
It doesn't stand to logic, i'll explain why: It's not that they're rated above Buch, but that the organization views all three of them as integral parts of the future on equal grounds, like you said, although Buch has some experience,they can't be rated above, but they can't be rated below either, and none of us has a knowledge as refined about them as the organization, so if they value them on equal terms, there has to be a reason.
You're both contradicting yourself and going on a tangent. Gonzales is far more proven than Bucholz, which is where you contradict yourself, and for the tangent, "pitching beats hitting" , i would concur with you if Buch wasn't the number five starter at this time, and they weren't hot on the heels of Aroldis Chapman. The bottom line is you need to give quality players to get quality players, specially in this case.