So many factors go into selecting a cat, you're going to need to give us more ideas on what you're looking for:

new or used?
budget?
1 or 2 people sailing?
your weight
how importance is performance/high tech?
where do you usually sail?
want to stay with no daggerboards?
uni or sloop rigged?
want option of spinnaker?

My nacra 5.0 has been a great boat for me, but the best boat for you depends on the factors above. In fact, I'm getting another cat soon but may keep my 5.0.

The nacra 5.0 can be sailed uni or sloop, has no daggerboards (instead has deep skeg symmetric hulls), and can be handled easily by one person but was designed for two. It sails well off the beach through surf. It weighs about 340 lbs and can be righted by one adult if the right technique is used.

Performance is similar to a Hobie 16, but I've found the hull design more forgiving (harder to pitchpole, thank goodness) and the tramp layout better (tramp flush with hull decks). I've seen guys who know how to sail the 5.0 really rip, and the Portsmouth rating is probably generous. H16 tend to be faster in lighter winds--I think they have more sail area; but the 5.0 seems faster in heavy conditions--hull design is easier to push harder, less sail area(?).

Downside of the 5.0 is that there just aren't many of them around compared to H16s. I haven't sailed the 5.2 or H17, so I can't compare it to those.

Used ones can be had for 1000 to 4000 (you get what you pay for); new ones (now the Nacra 500) are probably about 7500-8000--these have more sail area, I think, than the 5.0.

Good Luck