You can always just limit yourself to 16 tracks.

There really is no difference, other than you would have the flexibility to add more if needed. I mean, I understand not wanting to be overwhelmed, but having more tracks is never a bad thing. I generally only use 8-12 tracks, depending on the project... but love that there is more in case I get into writing some crazy weird song that requires more.
I generally record everything in stereo, just to get a fuller sound... hence the use of more tracks. Otherwise, I would only be using 5 or 6 tracks. Again, just limit yourself. No sense in paying for a limited keyboard, especially since most newer keys use 64 tracks or more. You are just going to run into issues then with limited sounds, that you may or may not like.
If this really is your direction, you could always go with a Yamaha SY99:
http://cgi.ebay.com/YAMAHA-SY-99-SY99-Keyboard-Synthesi... -
http://www.vintagesynth.com/yamaha/sy99.php or something like it. They are older, but still great workstations and perfect for what you want(16 tracks).