100mm macro: USM vs. non-USM

I am in a dilemma over getting USM vs. non-USM version of canon 100mm macro lens; I am getting non-USM for around $100 less. Apart from faster focus of USM, are there different optically, or is there any other benefit that USM version adds?

get the USM! the non USM is very slow focusing. you will have to MF the non USM lens if you go that route

I have the Canon 100 f/2.8 USM Macro, and I love it. Pay the extra, and get the USM.

I had the non USM version for some time.It's staggeringly sharp ..and the USM version is said to be just as good or maybe better.
The non USM version does focus pretty quickly at normal distances,it's just when you try to use AF for macro distances that things get silly (but why use AF for macro?it's pointless)
Probably the deciding factor should be wether you want to photograph sports with it.The non USM just wouldn't focus fast enough for that

Hi.....

I dont have the CAnon, but do have the Sigma 105.......If the glass is just as good.....wouldnt you be shooting macro in manual mode 99% of the time anyway?

Just my 2¢

Show me a young Conservative and I'll show you someone with no heart. Show me an old Liberal and I'll show you someone with no brains. - Winston Churchill


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300D
Sigma 70-200 2.8 EX
Sigma 105 2.8 macro EX

The Tamron 90 macro is considered by many to better the Canon 100.
I am undecided