Quality, and type of protein really don't have much to do with each other. Much of it is based on production procedures, and what you are looking for in a protien. Ion exchange Whey is generally the most bio-available, but quality will vary from one factory to another. Casien, while not as bio-available, gives more sustained amino releases into the blood (reason why people say to use whey with milk, quick/prolonged release).
Blends of high quality protiens are better than any one.
Whey also is liked due to its high glutamine content.
It's pointless to answer the poll IMO because it makes no sense. Its like saying what is the best food?
Some cheap protein is cheap do to low quality (ie not having advertised content, low bio-availbility...ect). Others are cheap because they are bought in bulk, or sold in bulk..ect. IMO pay a little more and buy something that is tested by an independent lab, or is known to be high quality. And I don't mean that hyped up muscletech shit....
-FC