I was going to go aluminum because mine were bent. My originals were 1-3/4 x 1/4 wall & they bent shortly after I built them. When I looked at the weight savings versus cost, I couldn't justify it. Instead I went 1-3/4 x 3/8 wall and then drilled & tapped my 1-1/4 shank joints in instead of having to weld in bungs. I couldn't find anyone who had bent their links using that size and so far, neither have I.
My steel links weigh 6 pounds more than aluminum would. I forget the cost difference but it was significant, like $75 more.
Interesting that you're liking the MTR's. I still don't know what I am going to do when I get rid of the Krawlers.