Just upgraded from a FZ6N to a FZ1N ABS; both are cracking bikes. The 600 is more than enough as a first 'proper' bike as the FZ1 is an absolute animal! I would recommend the ABS version - if only because you'll have less trouble selling it on when you want to trade-up. There's a reason non-ABS bikes are discounted! The ABS is a useful tool to making you keep shiny-side up in those circumstances where you've mis-read the road and hit a unseen greasy spot at the wrong moment. If it saves you bust-up bodywork and bruising (god forbid worse) then it has got to be worth it! Ignore any advice to the opposite - it tends to come from luddittes who mourn the passing of plunger frames, drum brakes and carb tickling.
I would also recommend the Fazer over the N if you plan any long distance work - it's not just the half-fairing but the lack of bungee points (on the FZ1N) as well. It becomes more relevant when you find out the FZ1 tank is lumpy and half of it is plastic - I haven't found a decent-size tank bag that will fit properly. If you just want to go play in the traffic then there's not much between having an N versus a Fazer. The only drawbacks are the clutch cable getting in the way of the ignition barrel on the FZ6 - really annoying after a while unless you zip-tie it back against the handlebar risers. The other is the traditional Yamaha gearbox (clunk and click every trip). The FZ6 also has those underseat exhausts, which could make using off-the-peg throw-over soft panniers awkward.