The ZZR is quite capable of 600+ mile days, with a Corbin saddle, and, for your height, a set of GenMar risers. I ride two-up, and log an average of 47 mpg., 50 solo (LOVE those carbs!!). I've not had the pleasure to try a Nomad, so I can't compare 'em, but have ridden "cruisers" in the past and can't stand all the weight on my butt. The Big Z gives a good balance of butt, leg, and wrist weight. It handles like a mid-weight sport bike, and goes like it was tied to a 'Busa...
Riding at 70-75 will give you about 5-5250 rpm, and no buzz (of that kind!). Pillions will complain about the non-insulated rear pegs, but a good pair of boots will remedy that.
To date, there are no worries with this machine, beyond a decelleration wobble that seems to be caused by the stock Bridgestones after 3-4K miles. Replacement (usually done under warranty) with Dunlop 220s (as the '03s come stock) seem to be the remedy.
Best bet? Keep the Nomad, and buy the ZZR too.