Hi all,
I was having this debate for my Nikon D7000, unsure of the canon pricing, or spec, for these lenses, but I decided on both.
The 35mm was £105 and the 50mm £85(eBay) I had my best friends wedding yesterday and did not want to use a flash, for a couple of reasons. The first is I only have the on-board flash, which is not great and secondly I wanted to be unobtrusive. The 1.8 aperture on both lenses meant the need for one was not required until the band in the late evening.
I shot with the 35mm indoors, while getting ready in the morning then changed to the 50mm for the day. I am used to zoom lenses and so laziness definitely sets in, however with both primes you are forced to move and generally become more creative. Just to point out I have a crop camera, 35mm being more like 52mm and 50 being 75mm.
They are both fantastic, the 35mm is great in more confined spaces and when the area is more open the 50 replaces it. This was the first time I have used a prime and the results are awesome.
I love catching facial expressions, pose etc, I mainly have it for my children, but on days like yesterday I shot groups, confined actions and if you compose well and preempt the situation you get great photos.
I read 35mm is great for street photography and casual shooting and 50mm being better for portraits. I take all advice with a pinch of salt and the reason photography is great is because there are no rules, you do what you want... The lenses are what they are, to that stick to the facts, they have a different field of view, what they can be used for is up to you.
Again, indoors the 35mm is more useable and outdoors the 50mm. It's about what you look for in your pictures. Unfortunately nobody can give you a definitive answer, only share their experiences, so if the budget allows get both, because you know if you order one you will wish you had the other.
Hope this helps with your decision.