Well from a business standpoint, it wouldn't hurt to diversify your web site earnings potential. There are quite a few PPC programs out there to choose from. Its finding one that can compliment your site that's the challenge. EPC's may be higher with O's programs but I've found G's programs to initiate far more CT's. I firmly believe its all relative to individaul sites. That's why I don't put too much weight into averages on a whole, unless you are lucky enough to determine stats for your niche.