I own the EF 50mm f/1.4 and use it on a 5D Mark II (Full Frame).
The advantages of the EF 50mm f/1.4 over the EF 50mm f/1.8 II:
- Two-thirds of a stop faster, so it lets in a bit more light when shot wide open. This helps to blur the background more, but the difference isn't huge.
- Has an 8-bladed diagram versus 5-bladed, which makes for more pleasing* bohkeh (out of focus objects are a bit rounder).
- Somewhat better build quality. The f/1.4 can be a bit fragile, because of it's "micro" USM motor (try not to drop it!), but the f/1.8's body is completely plastic, including the mount.
Another option is the original
EF 50mm f/1.8, which was made from 1987 through 1990 (often referred to as the "Mark I"). It has better build quality than the current version, including a metal mount, plus it has a distance scale. You can find them for sale on ebay and other places (fredmirdanda.com, for instance). Don't go paying $200 for one, though. I got one for my cousin last month for $120.
Do some searches on each lens (dpreview.com, fredmiranda.com, etc.) for reviews and sample shots. Go to a camera shop and try 'em out. No one else can tell you which will be best for you
. Just remember: a "better" lens (or camera) doesn't take a better picture. It's what you do
As for lens compatibility, if you think you may go to "full frame" in the future, then buy "EF" mount lenses, instead of "EF-S." Canon's EF lenses will work on any
"EOS" SLR, film or digital, while EF-S lenses work only
on APS-C digital SLRs, like the 60D, 7D and all the digital Rebels. The only issue there may be if you want something "ultra-wide" (less than 24mm). Due to the 1.6x crop factor, EF lenses don't provide as wide an angle of view on a APS-C body, as they do on a full frame body. For example, a 20mm EF lens is equivalent to 32mm on an APS-C body (20 x 1.6 = 32). Therefore, all the EF 50mm lenses are 80mm on the 60D!*
- Everyone's opinion is different.