
To the CCF
I use a Canon T3 for coin pics myself. I use the 18-55 Macro with tube extenders. I find tethering it to the computer and using a sturdy tripod really helps.
The lighting and background color you use make a huge difference as well. I use a black background with 2 desk lamps. One is a goose-neck OTT Lite and the other is a "clamp" on swinging arm lamp with a 5200k bulb.
Try experimenting a little and you should do fine with yours.
Oh yea the T3I has a wireless downloading feature and a faster shutter speed for live action shots I don't think there are any Other differences between the T3 and the T3i