FWIW, back when I was doing gun repair work full time I had Marlin lever guns with broken ejector springs and/or extractors come in fairly regularly. Certainly more often than I ever saw on 870's. Never did have a Marlin come in with a broken buttstock so I'd have to say it's not the weakest point in the Marlins and my money would be on an 870 for dependability/durability over a Marlin lever.
