Go ride some bikes.....
you can't beat actually riding the bikes you like the look of, preferably on similar roads and at equivalent price points. My idea of a harsh or compliant ride may bear little resemblance to yours, likewise, handling, climbing, etc. Your weight, riding style and preferred equipment will all factor in as well.....
If you're in the slightly used market, look out for signs of crash damage/repair.
Like Khuon, I am a bit wary of going into the whole frame material debate (yet) again. Ride some bikes- and buy the one you go back to and want to ride all day!