Good morning BSGfan.
In simplest terms, acetyl L-carnitine is better able to cross the blood-brain barrier, due to the acetyl component. Especially as we age enzyme production required for acetylation becomes limited. This would adversely affect both the metabolism and efficacy of the L-carnitine component. Otherwise carnitine resides mostly in muscles and would not be uniformly distributed throughout the body.
Of course, the first line of defense against statin damage is always reversing the depletion of CoQ10. Otherwise, I would use acetyl L-carnitine exclusively, but especially if you're older and have suffered statin-induced cognitive loss. If cost is a factor, you can purchase acetyl L-carnitine as a bulk powder.
Here are 500 grams of acetyl L-carnitine for $24.99, or good enough for 1 year of supplementation at 1.5 grams a day. You will need to cut and paste this link into your browser.
*http://www.bulknutrition.com/advanced_search_result.php?keywords=acetyl+l-carnitine+powder
Just place a little in a drink, or swallow it with water. I equate the taste with that of pungent and slightly rotting limes.
A slightly packed 1/2 teaspoon should equal approximately 1.5 grams. I would also combine carnitine with alpha lipoic acid. This would help to decrease the oxidative stress created by such large doses of carnitine, among other beneficial things. Together they have a very synergistic effect.
I've posted this as a general answer for anyone who happens to come across it.