I was at the NE boat show and had this discussion with one of the Grady reps. Outside of cockpit layout and the extra 15 inches, I was told the hull design of the 205 is updated and optimized for a better ride. I have to say the 192 can be a bit choppy, but you can always slow down to 7 knots and pretend you're sailing!
BTW, I think the 192 is the best, most versatile 19' outboard ever created.
My $.02
"The boat can take a lot more than you can."