The magnum has much potential beyond and above the LA, namely roller cam, 1.6 ratio rockers, and the heads, although crack prone, are superior to any LA casting. Personally, I wonder if the cracking issue wasn't less of a thing than the internet made it out to be, namely because EQ or somebody would still be cranking those out if there was money to made there. I almost wonder if, for a many magnums are still out there, if the ones with terminal cracking have been filtered out. Disclaimer: I've not read up on why EQ got out of the game.
If I'm going V8, I'm going aluminum heads. If performance is what I'm after, do it right. If not, a bone stock slant 6 is fine.
All that said, I've vowed never to run another LA, but if I swap again, it'll probably just be to a gen III hemi, namely because they're still in production so the parts will be around longer than the magnums, but also if it's a power game, they win.