I say if you wanna sail, buy a sail boat.
Everyone has different comfort levels and ideas of fun. We bought a 26 footer as our first sail boat and it has been a perfect fit for us. It is small enough to not be intimidating and big enough to give us the comfort to make sailing fun for us. Because it has a heater we can sail year round where we are (the pnw) and just have to take turns ducking below in January to warm our hands.
If we had a 18 footer we would have only sailed 3 months of the year, where's the fun in that?
However if I was living where the water is warm I would have a Hobie for sure!
They are fun!