Is there any difference in protein that you can buy in bags, these big bottles, or tubs? These tubs, or basically plastic cubes look kinda cheap, but I guess that as long as the protein inside is good, it should not matter - right?
Some companies sell the exact same protein in bags, jugs, and tubs. Sometimes it's just the quantity inside. The packaging doesn't matter. Like you said, it's the quality that matters.
Many times you can even get better protein products sold in bags than in tubs - what matters the most is the actual product inside, not the packagins, since there can be many different reasons for the manufacturers to use one packaging, or the other.
The packaging makes no difference. What you want to do instead is make sure you are getting a pure whey isolate product without any fillers or other crap added to it. I really like Isolation made by N2BM...especially the Columbian Espresso and PBCrunch flavours...