The 35 and 28 are very close in range, and f2 vs 1.8 is really close also. The 28 is faster to AF. It is a bit soft form 1.8-2.5. So if you are getting it just to shoot wide open, you really are not gaining much. I like to walk around with primes, and stopped down to 2.8-3.5 it is a very sharp lens. As shooting outdoors with 1.8 is not that feasible on a sunny day.
On crop bodies, 28 is not very wide either. So if you want to shoot wide, the uwa would be a better option.
Traveling is my passion, so I am a major Frequent Flyer.
Canon 60D, T1i/500D, Eos 1, Eos 630, and Olympus epl-1. Current Canon Lenses ef 100 2.8, ef 85 1.8, ef 50 1.4, ef 28 1.8, ef 50 1.8,ef 28-135, ef 70-300, ef-s 18-55, ef-s 55-250, 500D close up lens. Current Olympus lenses oly m4/3 14-42, oly 4/3 35mm 3.5 macro with m4/3 adapter, panasonic 45-200, panasonic 20 1.7. And a Part time Pentax K-X shooter.