Honestly, which ever you get the better deal on would work if everything else is the same, the power output post tune, with the same turbos is going to be more or less the same. The LMM is easier to change injectors on and does not have the same head gasket issues as the early LB7. The factory turbo, if you would be using that on the LB7 is fixed with a wastegate and the LMM is a variable geometry turbo, so spool is faster but more moving parts. The LB7 is considered by many to be a stronger engine though in therms of the pistons and rods, so if you do not want to get into the bottom end the LB7 can theoretically take more power before you shorten a rod or crack a piston, though if your making this kind of power you should really build the bottom end anyway. the LMM will run higher slightly fuel rail pressure as well, but again, after turning and supporting mods, the blocks are pretty similar in performance so if one is significantly cheaper than the other, get that, if you want power without a bottom end, the LB7 is probably a slightly better option, If you want ease of future repair, the LMM is probably a slightly better choice. Given its going in a car with a huge engine bay though, im not sure the LB7 would really be too much harder to work on, though there is a good bit more disassembly required to R&R the injectors. Lastly, the LB7 (if its federal, which most are) will have 0 emissions equipment on it, so that might play into your decision if you dont want to get / fabricate the extra hardware to delete the LMM, since im assuming you dont plan to run a DPF under your Camaro.