The practical difference is that when you supplement with AA's you transfer a lot more money to supplement companies. Looking at the back of my
GNC brand 100% whey it points out that 1 scoop has 21 grams of protein of which 1.3 g are Isoleucine, 2.3g are Leucine and 1.2g are Valine (these three are the BCAAs) for $0.81/serving (at the current GNC.com price).
Alternately, i could get "
GNC Pro PerformanceŽ RapidDrive™ BCAA 5000" which has... 1g isoleucine, 3 g leucine and 1g valine. for $0.70/serving
So basically for about the same price as the BCAA supplement you can have the whey which has the same amount of BCAAs and another 15 or so grams of other AAs to boot.
BCAAs are reported to have anabolic effects (and/or to reduce catabolism post workout). Many many claims are made for the impacts of specific AAs or AA combinations taken w/ various combinations of carbs during various pre/post workout windows ... My current takeaway is that it's probably beneficial to have a pre-workout protein shake and have a protein and carb containing meal within an hour after ending your workout and also to have some protein before going to bed.