I usually get in trouble when I give my humble opinion especially with others here that have much more experience than I do with Hobies. I have a Tornado cat that is very lightweight and very lively and exciting to sail. It reacts instantly to input from the crew. I also just purchased the 21SE last spring and have been having a great time sailing this boat. Here are the good things:

You can take 6 adults no problem and still outrun 90% of the sailboats on the water.

You can sail with two and generally outrun 98% of the sailboats on the water.

The wings add everything to a boat, especially in cold water sailing....

With the weight and additional momentum you can easily tack and jibe.

With the weight and wide beam it also allows you to drive the boat hard and have delayed reaction times in gusty conditions with less experience crew.
Not so good things, but easily handled if prepared:

Takes a little more effort to rig. Mast is heavy, but can be rigged fairly easily with two and is very easy with three. It should take no longer to rig than an 18. My son and I have it down to 40-50 minutes depending on conditions.

Width at 9'-8 1/2" is harder to trailer. I have been trailering full width and have not been pulled over yet, knock on wood. I also choose my route to be more interstate than highway or urban roads.

When the winds are above 25 mph, the boat is quite a handfull.

Harder to upright if capsized, but with a righting pole should be no problem.

Being heavy it is harder to to beach. Need catwheels or PVC ladder to move far on sand.
Bigger is better.