-bigadv takes much much longer to complete. In my experience it gives an extra 3-4k ppd but this goes down the more you use your computer (-bigadv can take 2-4 days to complete). So if you have a couple gaming sessions during that time the points advantage can almost be erased. -bigadv is best for a dedicated machine imo.
Edit: -bigadv also requires 8 threads (at least 4 cores + hyperthreading). I don't know what kind of rig you have but usually to fold bigadv adequately you need at least a 3.xghz i7 running full time.