I haven't decided which make to go for, that's part of my question. Most of the manufacturers I've looked at have transducers that are common to several different models.
I'll change the question......
I want to fit an electronics package that is fully integrated. Any recommendations on which package to go for? And, which transducer?
Joe it seems you are looking for a complete system so a lot more info is required for people to give advice I think. From your bio it seems this is for a big powerboat? How complete an instrument system are you looking for, ie do you include in that radar, chart plotter(s), autopilot etc? Are you looking for cockpit/flybridge repeaters, even of radar and plotter? What existing instruments do you have and wish to retain?
At it's simplest, if your question is about fitting a depth transducer whilst the boat is ashore, then you should know this can be done (afloat too) without drilling a hole by fixing it internally in a small oil bath in contact to the hull. Speed transducers will almost certainly need a through hull transducer.
<hr width=100% size=1><font size=1>Sermons from my pulpit are with tongue firmly in cheek and come with no warranty!</font size=1>