Its gotta be the Xone:92 for me:

Highest Quality Faders
Highest Quality FX (LP,MP,HP)
2 x stereo send and return bus

Its a popular argument about the effects on the 600 but imho the xone 92 has a wide variety of effects as they can be combined together nicely (eg HP/LP together = phase), plus you can bring 2 sets of effects on each channel together so they dont clash and if you feel like being fancy you can use the high grade x-fader to contorol these fx.

In my eyes the pioneer effects are good for a while then there is almost an embarassment towards using them, because at the end of they day its not very hard and they do sound cheap.

Two full stereo send and returns on the xone:92 so if your after the cheap effect sound (which is fair enough) you can add a efx500 / 1000 and a koas pad or any fx unit or create endless loops of effects.

There is a midi out on the Xone:92 which suggests theoretically you can control vst's from your mixer and bring them into your mix, however this is very clunky to be honest.

Pioneer basically used cheap faders and components on the 600 and when allen and heath dj mixer sales picked up they rebranded and brought out with higher quality fader (as this became the fashion) personally I would rather put my trust in a guy that hand makes products in Cornwall over a large corporate machine only interested in how to scale down the prices without it being noticed.