Nikon - body
Canon - full frame sensor
Nikon - wide angle lenses
Canon - tele lenses
Nikon - Flash system
Canon-Auto Focus Speed on Pro bodies
Nikon - Macro system
Canon-Low Noise at High ISOs
Nikon-1.5x on all DSLRs(For tele shooters)
Canon-Very stingy with pricing
Nikon-Always one gen. behind Canon.
i owned and keep the panasonic fz1 despite owning and trying out the flwg cameras during the course of one year... canon a95, nikon 5400, olympus c-5050
i sold off all of them and the fz1 is still with me;p
Doesn't matter as long as the images are nicer than Canon's (IMHO).. Canon sensors/image processing engine removes noise better but it also tend to remove the detail and thus making the pictures look flat. Then again, it might be the optics also, otherwise why would EOS users want to fit Nikon lenses on their EOS bodies?
Wireless flash system (Even the in-camera flash also can fire, not like nikon)
Flim-like colours (natural)
In-built AS (saves money, imagine getting IS or VR for every lens you own)
Very very very good built quality (Even their prosumer Dimage A1 and A2 uses magnisium alloy bodies)
Superior G lens series (Better than Canon's L, and also much more expensive)
Very low depriciation (comparing to Canon's ever changing cameras. and the 7D is still selling 1.5K plus secondhand on the average)
sadly, all this advantages are useless ever since Sony took over.