Great analysis by srm. Let me just add a few things to that.
We've had our H16 for 33 years and I've sailed with friends on their H18 several times. Both are very fast, but I'm not convinced that the "sensation of speed" is any greater on the 18 than it is on the 16. Minimal at most. I'm sure the 18 is faster, but you'll get a "rush' when going fast with either boat. I've only pitchploed once, but it was my fault - not the boat's fault. Just keep an eye on the leeward bow and get your weight back when necessary. At 190 lbs. you might be able to right the 16 by yourself without the use of any righting aids. Also, it's much easier to muscle the 16 around on the beach, with or without cat wheels, when necessary.
At 190 lbs, with a 120 lb. wife/crew - I'd lean toward the H 16.