Would there be any benefit to making French toast with a low cholesterol version of Egg alternative? Or possibly just using the whites for French toast? (I'm currently using the very basic 1 egg/3 Tbsp. of milk recipe)
There's not a lot of difference between egg substitute (e.g., Egg Beaters), and egg whites. So the options you mention, they are roughly equivalent to one another.
The obvious thing both of these substitutes are missing is the yolk. An egg yolk adds a LOT of flavor to this sort of cooked egg dish.
In a french toast, whereas egg white is soaked up by the bread and creates a fairly unique texture, the egg yolk is the key to the flavor and it is what makes it rich. I think the egg white french toast is doable but I don't think it will taste wonderful.
In other news, may I quote Thomas Keller in relation to a recipe of cheesecake (again, paraphrased by me) - If you are worried about the fat, have a smaller portion, and don't do my recipe with low fat alternatives.
I think it applies to cholesterol too.
 I certainly haven't tried this since I'm already way too fat to eat any french toast anyways...