I'm in process of swapping the MW-pump to a M-pump in my W460 G-Wagen. Plan is not to get a rubber burning beast but a modest daily driver, so max 150hp. Fuel economy is also important.. if you can mention G-class and fuel economy in a same sentence.

I could get 6mm elements from 606 pump for free, or pay about $35/piece for the 7mm elements.

Is there any advantages to 7mm elements if I'm not after big power? What I've understood, with 7mm elements I could get more low end torque and better fuel economy..? Is there any downsides?