Shooting through the hull will reduce the range of any transducer, but if you are just looking for shallow-water numbers, that won't matter to you.
I was used to sailing with no depthfinder and then ignoring the numbers (damned numbers, always in Arabic never proper Roman numbers, either ?!) until one year when I couldn't figure out where we were. Moonless night, too much background clutter, and then I realized "_ _ _ " didn't mean a dead depth sounder, it meant "my brains run out at 199" I was over the main channel in over 200' of water and that was easy to spot on the charts.
So using a through-hull, or a sounder powerful enough to reach depths you may not normally be interested in, may have some advantage at times.
The downside of course is hauling and drilling and sealing.
And how come no one makes a depthsounder, or any sailing instruments, that use proper Roman Numerals on the display, for the westerners among us?