I always found 50mm lenses to be too long on APS-C cameras, except for classic portrait. If I was you, I would go for something even wider than 35mm.
I'm always recommending manual focus lenses and I know they don't fit everyone's needs but, if you don't find a problem to use manual focus, the Zuiko 24mm f/2.0 is a killer lens. Mounting it on a 50D, you'll get the equivalent of a 38.4mm on a full-frame camera, which is close to the best focal distance for general use (35mm).
This little Zuiko is much better than the Canon 24mm f/1.4 L (MK1) in the corners and I found it to be as sharp as the Zeiss and Leica lenses I used to have.
Considering the options you mentioned, i would go for the 30mm f/1.4, since it's wider.
The Canon 50mm f/1.4 is a very good lens, but it's not excellent for a 50mm.