I have used a Humminbird Fishin Buddy, on a inflatable. It was ideal, because the whole unit sits outside the side of the pontoon, no cables to run to battery and transducer - the rechargeable AA batteries are inside the unit, and the transducer is on the bottom of a shaft below the unit.
It worked ok, but not above about 10 knots, because the water pressure on the unit became too much, and the shaft had to taken out of the water (easy to do). Before getting one of these, should check how long a shaft is need to get into the water from on the sie coaming. Can get a longer telescopic shaft I understand. But, if needed longer than the standard fixed length, the speed restriction would be even worse, because there would be greater force ona longer shaft.
I now have a 13 foot aluminium boat, and use a Garmin 400C, a conventional setup with transducer under the transom, and cables from there to the unit and from a battery to the unit. As I dont have a battery for the motor, I have a small 12v (7AH) rechargebale battery, in a plastic box, inside the gunwale under the coaming. Finding a suitable place for the battery has been hard - the first place under the front seat, let rain water into the box; it needs serious protection from water seapage - now i have it in a simple plastic box with push-on lid; seems to be better. The battery goes 3 trips between recharging, ok.
Having the transducer on the transom is a pain - as it is vulnerable to being hit by something, eg when mucking around by a ramp or beach.
The Garmin 400C seems to work ok, at speed say about 20 knots - but i am still trying to get it tuned, to actually show fish sign.
It seems to me, its a compromise - the Buddy, on the side, would be far easier to set up and manage, and would be much more convenient - but need to be taken off when at higher speed.