Difference between these 2 Canon 75-300mm lenses?

[Laramie]

I know they are "cheap" but I'm a law student so I can't put money into expensive stuff for a little while but I still need a zoom lens for wildlife, rodeo, horse shows, etc. I'm not sure what the differences between these are. Thanks

Canon 75-300mm F/4-5.6
http://www.jr.com/JRProductPage.process?Product=20372

Canon 75-300mm F/4-5.6 III
http://www.jr.com/JRProductPage.process?Product=20371

[05Xrunner]

1 has USM motor the other doesnt.
like the other threads about this lens...I suggest the Sigma 70-300 APO DG..pretty much the same price but is better then the canon one

[Laramie]

1 has USM motor the other doesnt.
like the other threads about this lens...I suggest the Sigma 70-300 APO DG..pretty much the same price but is better then the canon one

Great I will check out that sigma thanks!

[klinz]

i agree with runner above. sometimes you will get a decent shot like this
http://www.pbase.com/klinz/image/50665213
but most times you will get a murky mess. i have the III Version and the purple fringing is horrid whenever you point it towards the sky.

[Tee Why]

Another vote for the Sigma. Wouldn't recommend the Canon 75-300.