circular polarizer questions

Hey guys and gals,
I need a quick primer on circular polarizers. The local store (Calumet) has a super multi-coated 72 mm for $114.99 for my Canon 28-200 lens.

It's the Calumet house brand made for them by Hoya.

Since this 28-200 lens is basically just my walking around lens I figured it would be ok.

Does anyone have any comments on this potential purchase? When I look at CP there are a lot of them.

What's the difference?

Thanks!


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equipment:
Canon 20d with battery pack, Canon 28-200 lens, 580-EX flash.

I would HIGHLY recommend you get this instead and Im sure most others will too.

Thanks!

Sorry fo the stpud question but why is the B+W one better? (I'd like to learn a little something)

Thanks again.