Both are good turntables. You get what you pay for though, if the NAD has been taken good care of it would be the better overall turntable and give you more upgradeability (better arm and all the Rega P2 goodies will work on it).

I believe the model should be either 533 or 555 for the NAD however, with the 555 just being a newer version by my assumption. I really haven't been able to get much info on the 555.

As far as the price on that NAD... I could get a 555 new for $500ish (USD) which is more than you're going to pay for that, but not much. I don't know the state of the market for this kind of gear in Canada but you're paying pretty much the same to the new US price for that turntable (currency adjusted, I'm not that dumb ). I'd find out what the new price for one of those is in Canada, it's a demo so give it a thorough going over and base how much you think its worth off that. I personally would expect it to be a fair bit less.

edit: Ok i looked a little and your Debut is about $60USD more than it is here after the currency change. Based on that your NAD is probably still too expensive, but not as bad as I had originally thought