Canon 100-300 mm f4.5-5.6 USM

[Chode]

Can you tell me more about this lens? Is it OK for the money? (350$)

Which one is better:

Canon 100-300 f4.5-5.6 USM or,
Canon 75-300mm f4-5.6 III USM ?

P.s.
please, do not recommend any other lens! I am considering only these two!

Thanks.