Originally Posted by Hudsonian
When considering whether you are a good fit for a dinghy, ask yourself, "Am I up to the physicality required of dinghy sailors?" Are you physically active? For example, do you hike, cross country ski, or bicycle? Unless you enjoy physically demanding activities, you are unlikely to enjoy dinghy sailing.
If you fit the profile, you will find that sailing a dinghy is more invigorating, develops skills faster, and costs less than other types of sailing.
I enjoyed Dinghy sailing for years, and did none of the aforementioned activities. However, I horsebackride, and am pretty active. With that, I totally identify with the OP... I get cramps like mad, and they are extremely uncomfortable. I've gotten them sailing, and after going for a swim (very unsettling to say the least). First might I recommend some of the "leg cramp" meds... they are homeopathic (vitamins), and seem to reduce the pain of the cramps or eliminate them.
Second, I think he ought to consider a keelboat. If it's about racing/go fast, any number of boats will do, but if it's class racing, then perhaps a J/22. If it's just "lets find a faster sailboat that I can be less concerned about leg cramps" then might I recommend a Capri 22. They are cheap, plentiful, and sail really well. It's a current boat, with a current class, you can buy them used all day long for about $5k (with working motor and trailer). If you get the Tall rig fin keel, they are also quite a lively boat (speed). If your area gets decent winds, stick with the regular rig fin keel... if you will be trailering lots, then get the wing keel.
Tons of other small keelboats to consider, all over the spectrum. But seriously, I think a keelboat is in order, just something a little bigger than a dinghy.