Drop-in filter: buy canon or canon holder with B+W CPL?

I have been researching the field for a while now. Have seen sme options - like cutting a gelatin filter film and sticking to the one already included with the lens. Who has gone the other way rather than buying canon polarizer: a Canon drop in holder and B+W filter?

Ok, since no one knew - I bought one. It just arrived.
There is a Canon protective filter already screwed in that can be replaced for any 5mm thick CPL.
I am not sure about 7mm ones, maybe they will be alright, maybe not.
What I don't like - the filter holder is plastic, actually the whole thing is very light and feels cheap. The only metal about it are the two knobs to pull/push it in the lens. Is the other holder with CPL filter same built?

Now I will be buying B+W one from Hong Kong and post some pictures later.

To finish this one-man quest on Canon drop-in PL-C 52mm vs. holder with B+W CPL:

The B+W filter appears to be half a mm thicker in diameter than the holder, mostly the threaded part, which prevents to freeley slide it inside. I managed to squeeze it in, which I highly don't recommend, as plasticky build of the holder may break. It was also a lot harder to take it out. For certain there is no abaility to adjust the CPL during the shoot, thus confirming the long awaited conclusion: GO CANON!

I am not sure if it would have worked with other filter or not, but definitely don't try with B+W. Besides the thickness of the filter being only 5mm, it is already almost the maximum that can slide in the lens.

Hopefully this can help others to make the only choice My Canon CP-L is in the mail.

I use the drop-in CPL from Canon for my 300. Not sure if B&W is better but the Canon works great.