The guy who runs the marina I used to work at has a work boat that he rigged with a 90hp E-TEC. He has a contract w/ the Army corps of engineers taking them to and from the marshes several times a week. All of last season in total, He used 1 1/2 gallons of xd-100 oil. Not too shabby if you ask me.
It will consume more of the xd-50 (less expensive oil). So in my opinion, it's worth having the motor programmed to run on the xd-100 oil.