Who actually uses the sampler on their motif?
Of my friends that sequence, most of them use software (e.g. Reason, Cakewalk, etc...). Proponents of on-board samplers support the fact that you can sequence wherever your keyboard is. But as far as portability, you can't beat a mac laptop and a lightweight controller if you had to work on the road. I've made a drum track on the bus on the way to a gig just using my Reason 4.0's redrum drum computer and some headphones.
As far as mixing/faders...that would be a big concern of mine. That's the main reason I haven't yet sold my motif 7 and gotten a motif rack. But themidiroom told me that you can control different patch parameters in a rack using the sliders/knobs on a midi controller.
I dont use a sampler at all
but as far as the fader piece
I am debating between the motif xs and the roland rd 700gx
I am leaning toward the roland because
I dont need the sequencer
but as far as a master controller controlling parameters
I would rather just have it on the board I am playing
in other words I would rather have the motif board and move the faders right there
then to have a rack that I am controlling