At this point, I think all bikes within a class are probably 95% the same. The differences are so minor as to be almost irrelevant. Figure out what size bike you need - note, just because you ride a 54 or medium in one brand does not mean you ride a 54 or M in another. Then figure out which bike you think looks coolest within your budget, then buy it. You'll be happy.
If you're new at road bikes, you're probably not going to be disappointed in anything you buy.