4 Strokes, 2 Strokes, Weight & Convenience
I use a new Yamaha 4 stroke 4 hp. For me, it was the best compromise of power and weight. It also has a small built-in fuel tank for short trips with the ability to hook up to a remote tank if I choose to go for the day. I don't have to mix oil with this motor - which is a plus, but the 4-strokes weigh quite a bit more than the 2's. I think the EPA will eliminate 2 strokes soon and we'll all have to be using 4 strokes.
A R.I.B. is good to have if you want the high horsepower and want to plane. With a soft bottomed boat (rolls up/less space), I don't think the highest hp ratings are worth it, so we compromised with a 4 hp. motor that works on both our 6' and 9' dinghies. We don't boogie too fast, but then I am not carrying what I consider excessive weight on deck with my combination.
Each sailboat is different, each Captain's needs are different. So, you pays your money, you takes your choice. All in all, there are a lot of compromises to work through.