You know what, IMO a merc will take the most abuse, and still be the easiest to work on! Buy an E-tec for the wholeshot and 5 year dealer warranty. But when they break, its thousands, and a pain to work on. Buy a merc for ease of maintenace and reliability. (even when they break, you can often limp home). Buy a yamaha if you want heavy, gutless and electronic failiure boat anchor!
In a rental boat environment, we've killed almost 8 yamaha's, 2 johnsons, 1 e-tec, and 1 2005 merc 75 that went through a sandbar, overheated, and melted #1 piston. 2 of our verados failed oil pumps, but I managed to save them. 60 bigfoots needed headgaskets after many overheats and 1 failed fuel float. One of them was at 3600 hours! burns a little oil, but it sure doesn't owe us a dime!
But then again, these outboard engines normally operate between 4000-5500 rpm. Not a rotax running 7200 rpm and bouncing off the rev limiter, being run hard from cold, not being able to cool off, etc. Just the cost of having fun. If you want bulletproof, get a 587. You really have to be an idiot to kill one of those. The 951 is a ticking time bomb, just as long as you treat it like a princess and take care of her needs, she'll put out lots. But cheap out on her, and she'll drain your pocket book quick, and take half the motor when she blows!