For the OP - the frame won't make or break you on a century. I got my frame with the main emphasis on 60 minute crits, rock solid bottom bracket, super solid steering. They're aluminum frames, built for rigidity (the frames I have are 1450 and 1650 grams), but I am good on them for many hours at a time.

If you like the way the AR looks and you're not doing a century every week, go get it. You'll find that bike fit and your fitness will become a huge factor in comfort, more so than measurable shock absorbing characteristics.