I know the Zuma from reputation, but don't know much about the Derbi. Scooters in general are rather OK, but if you have $2000 to spend ... I'd recommend looking for a really cherry vintage moped. You will probably have better sales representation and work with the Zuma, but any repairs will not be easy for yourself. With an actual moped, you'd be able to get it fixed on your own. You could still save TONS of money (since most peds in great condition go for $300 or so). If you are in Wisconsin (form your IP address), you should check "Scooter Therapy". They have vintage mopeds most of the time. And they will repair them no problem. Also, they care Avanti mopeds.
Don't get me wrong, I'm not anti-scooter. I even have a Yamaha Razz. But I do think mopeds are a bit cooler. And you shouldn't spend $2000 on anything that is not a true motorcycle. It's just not cost-effective. My moped cost me $300 but was in very cherry condition and I've put another $100 (less than) to make a few modifications and such. You could probably get a nice Puch or Garelli very cheap and have it running for less than $400 total. Check them out.
Save the rest of that money for later!