7XL Vs 8L on 12 cells..which is better?

[Rtsbasic]

Hey guys, sorry if this has been debated before, but I've just brought myself an Emaxx, and currently have an 8L motor from a previous project I'd like to use in it. My limit is 12 cells (due to my Mtroniks Truck controller). Mtroniks say 45-50mph is possible, realistically I've been told 40-45mph is more accurate with an 8L?

So my question is, would a 7XL be more powerful on 12 cells? And would it have a higher top speed (if I wanted it)? I only really want 40mph or so but I'd like very good acceleration, and I don't know which one would be better. I'd also like to be able to gear that bit higher when I take it to a big field. I'm also guessing the 8L would give me longer runtimes because it takes less energy to spin its rotor, but I'm just guessing? About half my driving is done at part throttle when I'm just going for runtime but I like to have a lot of power on tap. Cost isn't an issue, because i'm in a position to sell my 8L for almost enough to buy an XL motor if it will work out better.

Also, what drivetrain parts am I likely to wear or destroy on 12 cells with either of these motors? I plan on picking up some idler gears from Mike soon, but I don't know if anything else will need replacing.

Thanks for any advice you can offer me :)