Can't compare with the 1700 Nomad, but just upgraded from my 9'er Custom to a 1600 Nomad (a little bit longer) and I can say the following (my opinions only, YMMV, and I'm responding before I read any of the other threads to keep my thoughts unadulterated) -
Looks - Nomad. I got a LOT of compliment on my 900, but I get WAY MORE on my Nomad.
Twisties - 900. The Nomad just doesn't flick around quite as easily, and I don't have as much confidence, at speed, in the corners with the Nomad, as she tends to "dance" a bit more. It's not unsafe, but she just doesn't seem to lean and settle as well as my 9'er did. The 1600 was the longest of the Nomad line, though, so the 1700 may be better. This could also be that I haven't dialed up the right settings on the air shocks/forks too. Swapping out for a heavier fork oil helps, so I've heard, and there are progressive shocks available too.
Highway cruising - Nomad. Not as rev happy, more passing torque/oomph, more solidly planted, smoother riding, less wind blown, better sound... FANTASTIC. Enjoyed my 9'er, but the Nomad just does the highway 200% better.
Mileage - 900. Hands down. 43-48 on the 9'er, average about 36-40 on the Nomad. Can be less with a heavy wrist. Higher displacement does that, and historically, the Nomad doesn't fare as well as some of the cruisers of similar size/power (i.e. Victory Cross Country). Plus, you have to use the higher octane gas to avoid the knock/ping, which costs a bit more, and can still get some knock/ping even with that. A fuel controller solves that issue though.
2-up comfort - Nomad. Duh. The wife didn't mind the 9'er, but LOVES the Nomad's extra comfort. There's more space for the passenger, a better riding position, and in my case, floorboards instead of pegs. Plus, stock grab rails and a much nicer backrest.
Storage - Nomad. Locking color matched hard bags. 'Nuff said.
Maintenance - Nomad. My 1600 has an extra oil check/change with the shaft drive, but the 1700 is belt. NO VALVE ADJUSTMENT. The regular oil change is actually easier too, IMO, but the 900 wasn't hard at all. I haven't had to mess with the brakes yet, though, and checking tire pressures is a bit tougher. Plus, you get Gadget's page (for the 1500/1600 anyway). BONUS
Braking - Nomad. It's bigger and heavier, but braking just seems... more natural. Even emergency braking feels better with those double rotors up front.
Accessories - Nomad. There's more juice available for the electrics (driving lights, extra brake/signal lights, etc.) and more space for the "add-ons", IMO.
City/slow-speed - Push. Both seem to handle just fine, and I don't see where all the hype about Nomads being beasts at slow speed comes from. I haven't had any issues at all. The Nomad runs a LOT warmer than the 9'er though. The 9'er is also quicker off the line, if you're into that, but once you get a bit into the torque range of 1st gear, that advantage disappears quickly.
Overall - Nomad. (but I wish I could have kept them both) If there's anything else ya wanna ask, let me know. I'm always willing to share my opinion, but again, YMMV.