Hi Steve,
You'll get a lot of opinions, but it will depend on what kind of travelling you'll be doing. I have a Tohatsu 4 stroke 8hp on a bracket off the stern. It's a little more cumbersom, spoils the lines etc, but it's quieter back there and easier to handly because you can leave it in situ if it's locked up. The reason it's back there is that it didn't fit in the well. Some people would rather have a diesel inboard, but it's horses for courses and personal opinion really.
It uses about 1 to 1.5 litres per hour, much less than a similar 2 stroke, but could do with being a long shaft, instead of a standard shaft. I'm looking at remote control and electric start, might make it less of a hassle over the back.
The way it is in this pic is how it stays, it never comes off the bracket.
Michael