since no one else has chimed in...
Asian Panax ginseng is most widely used medicinally in Asia and Eastern medicine (my acupuncturist feeds me about a 1/4 cup of this stuff raw before going to work). Allegedly the benefits are that it helps conserve glycogen in exercising muscles, by increasing the breakdown of fat into fuel, allowing athletes to minimize fatigue and maximize endurance and is an aid to the male reproductive system, especially for men over 50, helping to balance and normalize testosterone levels. It also acts as a stimulant and gets your blood moving.
American Ginseng is less aggressive, butl purports a whole slew of benefits from insulin regulation to digestion benefits.
Siberian Ginseng is generally milder overall, more intended for children and the elderly.
There are several other inds too, but it'd probably same a lot of time to just look them up.
Anyway, by and large, it's not terribly important which kind you get. They have mostly the same effects with varying degrees of stimulation, so it seems.
Ginseng? 
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