Ma 2 cents
sorry do differ with lowj workstation versus controller/ computer
but... getting a controller/ soundcard/ pc/ VST and hooking it all together is laborious and just a big pain in the a$%. (Even though it is cool as heck once you get it right), The chance of all being wonderful on your first 15 tries setting it up is very low. I do this for a living and it had taken me almost 3 months to buy/ fix/ buy more/ get drivers/ reinstall yadayada e.t.c... to make my system work glitch free. These are concerns you do NOT need when just jumping into learning keyboards. You need your brain space for the art of playing well.
It sounds like you cats are trying to learn keyboards and do some elemental writing perhaps, so unless you are about to embark on serious recording or need pretty lights all over your desktop, get a good stand alone workstation - second hand on ebay or ask and look around here - Should be between 500 and 1000 SG and they are awesome song palettes as well - in fact some can really inspire creativity and learning.
The piano sounds on high end workstations are fine and some have killer stock piano samples.
Some good second hand workstations to look out for are:
Korg Triton family of keyboards (get the piano card though, stock piano is crap)
Roland XP series - old school now, but has some great pianos that you've definitely heard alot if you have had your radio on in the last ten years
Yamaha Motif - (more expensive likely) hands down the best stock piano sound and some very cool creative functions for writing songs and arranging. This keyboard is a good argument for preferring a keyboard with "stuff" in it over a midi controller with a computer - even when you know exactly what you are doing

.
As with anything, the newer the more expensive...
ma 2 cenz