Last question first - you feed the horse when you have enough posts

Now why did I buy the Motif (SWMBO asked the same question) well in a nutshell it's a fantastic workstation with better voices then the Tyros some of which are XS (hence the name) ie expanded articulation which give you the most realistic sounds I've ever heard, they have velocity switching which means they sound different depending on how you hit the note. There are no styles as such but rhythm patterns are made using one to four of the 7000 arpaggios built in. You can load midi files as backing if necessary but you could only load them as songs to which you can add further tracks.
Multitrack recording is the easiest I've come across - you can make up to 16 patterns consisting of up to 16 tracks each per song, you can chain them together in any order you like, convert them to a song and add further tracks.
Patterns are loop based but songs are linear.
'Performances' are the nearest thing to styles and you can record them into patterns or songs. There are hundreds of performances, all editable.
There are thousands of voices and sampled voices. You can make , edit and store your own samples. The voices some of which have 8 layers of sampling can be controlled by the 8 sliders and knobs in real time, ie ADSR and DSP can be altered. They also act as drawbars on organ voices.
The Motif comes with Cubase AI4 and when connected via USB to the PC can be used as a remote control for the DAW. The is also an editor for the PC so you can edit sounds on the Motif.
Yes it can be used as a straight synthesiser too, I sometimes have midi'd it to my Tyros so that the Tyros R1 voice plays a voice on the Motif. You have to connect the 2 via audio too.
It's a fab piece of kit - the Yamaha site will give you a better description than me - I've only just scratched the surface of what it can do. I have uploaded a couple of songs recorded on it - nothing special just experiments .
I'm not a pianist (I can't even read music

) but the Motif Grand Piano is a belter.
Cheers
Spike