I road and raced a compact all summer. Just recently I put the road bike away and dusted off the cross which is a standard. Holy balls batman. I felt like a beginner again climbing. My legs were so sore I was shocked. The compact spoiled me and if you're looking for fitness riding spinning in a compact may be the way to go. However, if you're trying to get stronger and faster I'm convinced the standard will be the way to go. Hopefully by the start of next spring I'll be spinning up the hills in the standard like I did in the compact.

FWIW, riding in the 53 ring felt amazing.