JudgementDay
Legend
Following brands I have used and enjoyed:
ON Gold (havn't used in over a year), NutraPro, LG Lipotropic
My favorite powdered protein, but it is a bit on the more expensive side:
Trutein. It is a great blend of protein sources, and tastes damn good.
On the way I have 7lbs of Nutrex Muscle Infusion protein (did the buy 2lb, receive 5lb free sale).
As for most efficient then you should look into peptopro products, which is quite efficient and can be incorporated well into any diet. It won't replace your whey, but it provides a great immediate protein source. Primordial has a peptopro product called Maximum Absorbed Protein.
Glad you like the taste of Trutein I ordered some and can't wait to try it out. I still need to try MAP, looks really good.