Is there a salary difference between the 320 and 330? Or is it just a rostering difference? I had been on the NB for a good 9 yrs before I got my upgrade so I believe I can offer a bit of insight...
Take all the time you can get on the NB short haul. It will be invaluable in your career. From handling to decision making doing things 5 times a day will give you a lot more experience then doing it 5 times a month.
Safe flying.