My latest RD weapon is an XTR M900/M910. It seems to have a good balance of performance and durability. It is a medium cage to 32t.
For short cage applications that are friction, (or index), Dura Ace 7402 rear derailleur was my weapon of choice for years. I ran it with a 28t with no issues and even tried a 30t, but neither of us were happy with that combo.
These are about as bullet proof as I have found.
John