kinda a mix of both. Its unrealistic in the way that yu can do massive airs straight on to rails, but real in the way that its pretty hard to do large spins or anything over a double backflip.
Personally Im not to fond of it, i think its pretty jurky and there is no real flow to it at all. Plus the career part of it has no real purpose it seems, you just randomly find contests that have no story behind them. On a plus side though the outwear in it is pretty cool and varied and if your just cruising it can be fun.
I would rent it first if i was you.