Different types of protein...Isolate vs Concentrate

My weight loss support group just talked about the different kinds of protein and I thought it was interesting.

Isolate vs Concentrate

Isolate contains 95% protein and is more expensive and has a higher biological value(biological value is a measure of the proportion of absorbed protein from a food which becomes incorporated into the proteins of the your body.  It summarizes how readily the broken down protein can be used in your body cells)
It is lower in fat and lactose.  Whey Isolate is the highest yield of protein that is available today.  For lactose intolerant people, the isolate maybe better because it has less amount of lactose in the mixture.

Concentrate: This is about 75% protein and cheaper to produce.  Contains more "questionable" substances.

So overall, which one should I use?  Isolate is very pure buts its expensive.  Concentrate seems to be the staple protein that everybody uses.  I have been looking at the protein powder I have and its a mixture of both, mainly concentrate with added isolate.

There is also soy protein, but I am not a soy fan so I won't even go there. 

And I thought all I had to do was find a protein drink I liked that was high in protein.  I will admit I have not tried Whey protein...I am still working my way through my COSTCO light muscle milk(which I like but its a mix of concentrate and isolate).  I am afraid I may not like the whey protein but I don't know unless I try it

side note: I still need a battery for my scale...I haven't weighed myself since December 22nd and its KILLING ME!  Why can't I remember to stop and get the battery---UGH.