I think a lot has to depend on the size of boat/motor you are looking at. One thing I always here is to get the max hp that the boat is rated for and to get a boat that is 2 feet longer than you think you should get. You shouldn't use a large two stroke as your trolling motor as they don't like to stay in the low rpm's. There is some new advances in 2 strokes such as the Etech's and Optimax's, etc. I hear they get as good mileage as 4 strokes. Also make sure you have the appropriate dealer nearby to perform service. Two strokes are usually lighter, easier to work on, and less expensive, but can be louder and smoke more. They way you run and maintain the motor I think is the greatest factor in how your engine will treat you.