I've used both and they're both excellent mixers.
Got a DJM600 at home and it synchs with my CDJ1000, which is pretty clever. Excellent mixer and you can do all sorts of damage if you learn to use the effects properly.
(***try this at home: get a record going, set the effect to echo 3/4 (I think - the second one in from the left !!!), then turn the bass down and increase the echo effect - it acts like a drum roll. Try turning the EQ's all the way to the right really quickly and returning to the middle while the effect is on, you get a brilliant dub effect. Also try a spinback while slowly decreasing the level on the channel, some mad noises !!!***)