Regarding the through hull transducer, I'm sure it is much more sensitive when located properly. However, these models are also far more expensive than transom mounts to purchase and pay to have installed. I think there are other negatives worth considering as well. Pictures I have seen of these installations show that the transducer hardly sits flush with the aluminum hull. This would seem to create more drag on the hull as well as being a greater risk of damage from impact. One of the most versatile features of having a welded aluminum hull is that it can run shallow rivers and be easily beached without much fear of damage. I'd be too nervous beaching a boat with an expensive through hull transducer exposed on the bottom. That would seem to negate one of the biggest selling points of a welded hull.