I live smack dab in the middle btw WB and CB so I have been trying to figure this out myself. However, it is totally swell dependent. I think WB seems to catch swells with some north component better but still I get surprised with a friend's call sometimes telling me CB was going off after I had a sub par session at WB. I like the clear water at WB compared to the murky water at CB. And for the people that say WB is too crowded, that because they go to the piers or south side. There are plenty of bars in btw that are not crowded. However, I have to say CB is still my favorite b/c of a punchier wave, cheaper parking and its fun to see all the people with mullets (the hair style not the fish).
and let's not forget the Tiki Bar in CB - where else can you surf to live music?