I have the Canon 60D body with a Canon EF-S 17-85mm f/3.5-5.6 IS USM lens for walking around with. That's a nice zoom range and a little step up from the typical 18-55 'kit' lenses they make. I also have the Canon EF 50mm f/1.4.
But I really want a good prime in normal/wide range. I just sold a 35mm, which on a 1.6 crop camera is about 55mm, the old 'normal' lens on my film cameras. I never liked that focal length on my film cameras, I often felt like I was wanting to back up a little.
The 24 and 28 seem fairly similar, both have the newer IS capability and USM focusing. FF equivalent would be 38.4mm and 44.8mm, respectively. The 28 for some reason is about $50 less expensive.
I am wanting to use this for indoor 'snapshooting' as well as outdoor landscapes and architecture. Is there any reason to go for one over the other? I am really torn here. The 28 might be just what I want given my feelings on the old 55mm FF and the 35mm for crop I just sold. But maybe the 24 is a little more versatile? Decisions, decisions. 
Thanks!

They are both great lenses in terms of IQ, no doubt about that based on all the reviews I can find. The crop equivalent of roughly 45mm for the 28 is not all that different from the old film 50.
