I'd probably go Pro XS. The old 2.5 mercs would run like a "raped ape" as my old mechanic used to say, but longevity certainly wasn't their strong suit. On the higher HP, Merc seems to have gotten it right with the XS. I'm not sure there is any difference in the longevity now between the Merc and the Yammy. I've got a 7 yr old XS on my boat and haven't had a lick of trouble out of it.