IMHO there is no "best" CL. Too many variables among the resorts and CL's themselves, not to mention personal travel tastes, party size, touring styles, etc.
Poly suits us the best, but we have some of the young kids
@AngiTN mentions in her post (and since we overlapped there earlier this year I'm sitting here hoping mine weren't the cause of her "Others not so much" comment

). Prefer YC CL more than BC (YC CL is in our top 3 favorite) and we didn't enjoy BWI CL all that much from our one adults-only visit earlier this year (but it gets plenty of rave reviews around the DIS), just didn't speak to us and my feelings are more along the lines of
@focusondisney's feedback above.
I could write a novel on pros/cons of each but I'd honestly need a bit more info on your party size, CL preferences, reasons for booking CL, etc. to make any feedback valid to your circumstances.