I'm buying a compact (50/34) and I'm reconsidering getting a 11/27 or 12/27 instead of a 11-12/25 cassette. This will be for everyday training in Colorado, not just for some epic ride. My current 39/53 and 12/27 setup generally suits my needs (which is close to the 34/50 and 11/25), but if I want to be spinning at 90 rpm up hills I probably need lower gearing. BTW - my ftp is a lowly 250W . . . but gradually increasing.