The results posted by PP seem odd to me. I wouldn't be all that surprised to see one work better than the other, but what is actually being relayed as the research here just seems...weird.
The claim that it increases Nitric Oxide more effectively shows that it does so in vitro. Yet the rest of the study claims to be in in vivo. Why would that get changed for that aspect only? Is it from a different study entirely?
Also, the claim that it increases blood arginine levels more effectively, would make sense to me. One ingredient is providing the body excess amounts of L-arginine, so of course L-arginine blood content will increase more with that than with something that requires conversion.