Originally Posted by
ericcc65
Both of these would seem to indicate I should get the long cage. But I seem to recall some saying the total capacity doesn't matter much. Maybe it means I shouldn't cross chain, which isn't a good idea anyway, but sometimes happens on accident and wouldn't want it destroying things. It also surprises me that this is the case with the medium cage mtn derailleur, is that because in those cases the difference on the front chainrings isn't usually as large as with a compact crankset?
Not being able to cross-chain on a compact is a serious annoyance. A compact only has overlap on the last 2-3 gears, so if you can't use the small-small combinations, you're going to need to front shift significantly more often. Get the long cage and avoid the hassle.