yeah thats what vin was saying about the crop body. with a 30 it will damn near end up being close to 50mm right?
canon crop factor is 1.6 x 30 = 48mm
crop factor really makes no difference unless you ever shot film or full frame. all you know is that a 30mm is "really" a 48mm but what difference does it make to you? when you put the 30mm on your crop body, what you see is what you get so why sweat what the crop sensor does to your len's focal length?
the 30mm is 48mm, the 50mm is 80mm. when it comes down to it, crop factor is just a useless number that tells you how much smaller the crop body sensors are to full frame sensors.
my advise, pull out your 18-55mm kit lens. go to 30mm, try it out. go to 50mm try it out. whichever you like to shoot more with, get that lens. all else is pretty negligible.