The ArginoCarn has arginine in it. This amino acid when taken without balance with l-lysine may activate viruses...like shingles, or cold sores (Herpes simplex). I tend to avoid recommending arginine products (some magnesium chelates have this in it too), unless you intend to take l-lysine with it.

The GlycoCarn is similar to the first carnitine the HIV community used. (propionyl carnitine) Which is a glycine (2 carbon amino + propionyl which is a 3 carbon amino group). At one time years ago acetyl carnitine was not commonly available, but now it is.

For our purposes, I'd start with acetyl carnitine. I believe the others provide metabolic support in other ways. For example a source of glycine is involved in methylation chemistry, and provides the methyl group. Acetyl provides the acetyl to acetylcholine synthesis which is an important neurotransmitter in the autonomic and central nervous system.

Today there seems to be more research on acetyl carnitine in the medical papers, especially in regards to chemo damage prevention.

The GlycoCarn would be more expensive, but if you want the other benefits listed on this link, there is no reason not to try it.
http://en.wikipedia.org/wiki/Glycine...yl-l-carnitine
The extreme exercise and bodybuilding people seem to like this combo because of the nitric oxide stimulation.