L-Carnitine Tartrate is better for physical performance while Acetyl-L-Carnitine has been shown to be better for brain function and cognitive performance. As for fat loss, oral carnitine has a very weak positive effect, and it's mostly in elderly populations. Anecdotally, I know some competitive bodybuilders swear by injectable carnitine (obtained from veterinary supply stores), but take that with a grain of salt as I'm not sure how much human research there is on that. That being said 3g fish oil + 1g carnitine daily is good for general health, blood flow, brain function, etc. Just don't expect miracle results from the combo.