i just went thru the same deal with my new bike.

i'm just under 6'2"...all legs and short torso and arms. i ended up on a Cannondale 56. Yes, it's a little more drop than i wanted, but after a few hundred miles, it feels great. a 58 would have had too much reach for me, and the 56 fits me great. if you can handle getting used to a bit more drop, i say go for the smaller size. just my $0.02