I found this tid bit on the internet about All Clad. It sounds like both D3 and MC2 are 3 ply just arranged differently.
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I am looking into tri-ply cookware, including All-Clad and found this discussion in a search, so I hope you don't mind if I jump in with a couple of questions regarding the cooking difference in Stainless and MC2 collections.
If the graphics on the All-Clad site are at all accurate, it appears that the stainless on the inside of the MC2 collection is thicker than the interior stainless layer on the Stainless line, but then, of course, has none on the outside. I think it appears that both have similar thicknesses of aluminum and stainless, just distributed differently. The Stainless line has a thicker inner core of aluminum, and the MC2 has aluminum alloy on the outside...Are these differences significant? And by that I mean to the cooking performance, not the look. I cook on a Wolf gas rangetop and want to make sure of even heating, no scorching on the sides, etc."
I also found this and it looks like the newer LTD is lighter than the older LTD. I am still looking for where I read the original MC was thicker than the MC2. It looks like the MC stuff has been stripped off the internet.
And I should add it looks like the original LTD weights more than the MC2. Your logic seems to imply the LTD will be better. I don't think it is that simple.