Opinions on a B+W Cr Pl

[Photog82]

Right now, I have a Tiffen circular polarizer, 77mm slim mount. I used it on my EF-S 10-22 lens and was mildly unhappy with it due to that I can't stack filters on top of it.

Now that I own the EF 24-105L lens, I'm looking at buying a better filter for both lenses since they both take the same size. I'm looking at the B+W 77mm Kaesemann Circular Polarizer MRC Filter slim or the B+W 77mm Circular Polarizer Slim Filter.

What I'm wondering is:

• Does the slim really make a difference on the ultra wide lenses?
• Does the Kaesemann really make a difference over the non-kaesemann?
• Can I stack ontop of the slim filter?
• Does have it vignetting? I can't find an answer on this
• Is it worth the extra $100 that I paid for my Tiffen and over the second B+W filter I listed?

I have a 7D