I have a thru the hull transducer in back and I have a bolt on (for the trolling motor) up front. The thru the hull is nice, however it doesn't give water temp or speed, which is a bummer. If you want speed and temp (which of course costs extra
) I would think you would want to go with the external, screw on transducer.
If this is a glass boat thru the hull is the only way to go. At the Bassmaster at Ouachita the lowrance truck replaced something like 73 transducer over the course of the tourney. An external mount you always have to worry about knocking it off. If it is going to be on the bow of the boat hose clamp it right to the bottom of the motorguide. (or that other one)