Well, for me (mostly Y flyer), M&M works out because I had a lot of small hops < 500 miles (FMO-FRA, LAX-SFO, IAD-PHL etc.) and get 1250 miles on all of those (e. g. Sh*ttle SFO-LAX: 308 MP miles (status). For the long-hauls, the 100% PremEx bonus is nice, but I'd stick with the carrier that moves the metal I'm in most of the times, and that is LH for me.