Ideal size depends on how you use the boat. If you spend weekends on it, then you'll need less space. If you live aboard for extended periods, you'll want more space, because you'll need room to store more than a weekend's worth of shirts, shorts, socks, underwear and food, as well as fuel and water. If you sail long distances and in big waters, a bigger boat will have a more comfortable motion. If your sailing is mostly local, a smaller boat is in order. Bigger boats can be handled shorthanded, but it's more difficult to handle them. It's harder to tack or gybe a big boat, and to raise and lower and furl big, heavy sails. It's no fun to raise a big mainsail or jib by yourself on a day when the temperature is in the 90s. For me, for example, a 35' boat is a good compromise. It's designed to sail long distances and in big seas, but it also sails well in lighter winds, and it's good for long term living aboard, but it's small enough to be single-handed by an older sailor.
I could singlehand a 40' or bigger boat, but it would be harder work, and my boat does what I want it to do, so a bigger boat really isn't necessary, and would increase the cost associated with it.
Last edited by Sailormon6; 11-09-2011 at 10:10 AM.