There are differences in protein. Do you know why everybody used to use soy? BECAUSE IT"S CHEAP! Soy is an incomplete plant protein without all the essential aminos in proper ratio. What that means is out of the 20 grams you ingest, you're really only getting only 6-7 grams of useable.
Next up is whey concentrate. (The stuff used in most powders and MPR's). It has a lower percentage of usable protein than other forms such as whey isolate or cross filtered whey or even casien. Once again, it's cheaper. Protein Factory sells it for $5 and the isolate cost $10 per pound.
Manufacturers know that most people don't look into this stuff. That's why they use concentrate. It says "whey" and it contains so many grams and people think it's good. It's the stuff that they use in animal feed and processed cheese and deserts as a binder. It's the stuff they used to throw away when making fine cheese.
Organic whole egg is more expensive $12. And Plasma Serum is $43!!! BIG BLAST contains no concentrate. It's isolate, whole egg and plasma serum. That makes it a superior product in terms of potential muscle building.
Now if none of this doesn't matter to you, just buy soy or whey concentrate in bulk and save yourself a lot of money. But don't say there's no difference just because something mixes easily and tastes okay.