i use a compact record group with an 11/23 cassette. plenty fast enough for 50 kmh racing... 50/11 is a slightly bigger gear than 53/12 so you're up there with most of the other bikes. and if you want to go faster? SPIN!

the 34 is a great hill ring, but the 50 is not bad for short hills less than 10% if you get in the larger cassette cogs, which could mean perhaps less gear changes than if you used a 53 big ring. of course, it needs careful set up to avoid cross-chaining issues. (not a problem on my bike even with short chain stays) and i have the benefit of training on a single speed so mashing is my usual hill climbing mode...