I have stayed at all 4 mods. This is all a matter of personal preference, of course, but my personal ranking of the mods are:
1. PO-Riverside
2. PO-French Quarter
3. CBR
4. CSR
If staying at the CSR, I would probably put in a preference for one of the buildings closer to the food court as it is quite a hike if you are in one of the buildings on the opposite side of the lake. Actually, the pool/play area at CSR is quite nice. But for overall theming, convenience, etc., my preference is for one of the PO resorts. Enjoy your trip!!