Whey proteins..is there a difference?

I read alot of you like Optimun N's products. The local health store I go to always tells me to buy the Biox Why isolate as it is the best bang for your buck. He tells me it works the best and it's not pricey. My question is, is this true, as I also have seen those 10 pound bags of Optimum Nutrition :100% Whey Protein as well. Is this whey just as good, better, or not as good? I want the bigger bag of ON but not if it is not as good as the BIox whey isoalte. Please someone let me know as Biox also now has the slow release protein for nighttime in the 5 pound tubs as well.

I also did notice that the ON 100% whey has 22 grams of protien and 110 calories in its 28.4g srving while the Biox has 35 grams of protein and 128 calories in its 35g serving.