well, the actual black and whites of the keyboards i'm not familliar with, but i do have the rack version and i like it alot...but i'm doing a lot of sound design type stuff. as far as being a "groove synth", or a push play and you're NIN, it aint. it's the ultimate UDI (user definable instrument).
I like the fact that not only an amazingly powerful sampler, but i can combine the odd noise samples i take with the slew of traditional onboard sounds.(thus saving me time and memory in not having to take up any additional space sampling a string or bass sound.....

i will say this though, the effects are kind of weak,esp the reverb which adds a ton of noise at higher saturations and the sequencer is counter intuitive. on the up side, i don't have to rely on the effects for total sound design thanks to the ultra powerful filters and flexibility of the synthesis

so it depends on what you want....