As far as fuel consumption is concerned there really is nothing in it anymore between 2 and 4 stroke, There is alot more torque from a 2 than a 4 resulting in better take off etc obviously the torque range varies between manufacturers.
(advice dont go down the line of honda)
The power output the manufacturer states always varies slightly but obviously if it says it is a 200hp then in pretty much is give or take 1 or 2 hp.
To be honest If I was looking for an outboard around the 200hp mark I would look at either an Evirude Etec or Merc Optimax both great engines just depends what way you want to go.
Another option if you want 2 stroke performance from a 4 is Merc's Verado but obviously this comes with a weight penalty.
Hope this helps a little.