I bought a Nacra 5.2 earlier in the spring after sailing mostly on H16s. The Nacra is a much better boat (I'm biased). My friend who sails with me on the H16 says that the rigging on the Nacra is too complicated, but I think it is much better because you can shape and pull the sails from any direction you need to get the proper trim. I have found that the H16 (especially the jib) is limitted on trim options. Some more experienced sailors might disagree or maybe they have different setups than the standard H16.
I had to do a small repair on my boat last month that was a piece of cake to work with. I believe my boat is an 84 and it has solid fiberglass hulls. The hulls on the Nacra 5.2 are very solid compared to the H16. I have found that even though the H16 sits higher, both boats are wet in any kind of chop. Although, the h16 is much much more likely to pitchpole on you, especially with a second sailor aboard. My boat is the only Nacra parked on a beach that has about 10 H16s, 1 H14, and a bunch of sunfish/lazers. I don't have a problem sailing around with my friends on different boats. One thing though, if you do get the Nacra 5.2 and you sail with friends on H16s, make sure you have a flexible neck. You will be forced to look back a lot to see your friends sail.

-Rob V.
Panama City
Nacra 5.2