XS=Optimax=Direct injection=45% less fuel consumption at mid range cruise compared to standard fuel injection,also you never see visible smoke from exhaust.They weigh roughly the same as 300hp pro max,but about 100LBs heavier then 280 offshore.The revs will be less then the 300X so you just opt for the 1.62 lowers and go with a little more pitch.They are the only outboard that is allowed on Lake Tahoe