The PC3 has no pattern recording like you know from the Motif. It´s like a multitracker or tape-recorder. But it has the ability to do "riffs". Those are looped or non looped musical segments that can be attached to sounds. Those can be stacked 16 times with 16 different riffs for each sound and synchonized. You can start or stop riffs, or a bundle of them with keys, buttons, pedals, whatever, it´s free programmable. Some demos you see on youtube with switching segments on or off on a PC3 or PC3le (like tracks on a drummachine) are done this way. This can be nice for live or recording situations, since you can switch tracks on or off. You might also want to check my video on YT about "Groove Menues". It´s done the same way. All available riffs (sometimes segments from song sequences) are programmed to start/stop on a key. In this case used for drumbeats. In theory you could play whole songs with that, you just might run out of free riffs that had to be present all the time - and not one after the other like in a pattern mode. To have a new collection, you´d have to switch to a new setup with another 16 of them. In my video for the Kurzweil Forte contest I also used this in the last part ("dub space"). The background is completely played with this one setup.
But it´s not the same like pattern recording. If you are familiar with the workflow on a Motif, I guess you won´t be happy. It´s a different approach.
The sequencer is a working, but not the strongest or user-friendly part of a PC3. Though I never worked with the sequencer on a (my) Motif, it seems to be a better developed part than in the PC3 series. On the other hand, you can do different things with it on a PC3. For example you can attach sequences into setups that can be fired up like a sample with one key, while playing chords with the other hand. You can always have 16 of them the same time.

Thank you for the detailed reply Kaffimusic. I had seen "riffs" mentioned before but didn't fully understand them.

Though workable (and, from what I read of your post, quite usable!), I suspect you are correct in that ultimately it may not be 100% what I am after.

Workstation lineage is certainly different than "groovebox" lineage so I guess I shouldn't find it all that surprising most workstations don't really support this workflow. I suppose it's fortunate that Yamaha decided to graft on features from it's now defunct groovebox line to the Motifs.

Oh well... my roommate in college had a Kurz 2K and I always lusted after it. I was hoping to solve a problem AND fulfill my 20 year desire for a Kurz at the same time!

Thanks again.

Fulfill it
Seriously, the PC3(k) sounds different from any Motif or Korg. Once you realized WHY, it´s outstanding. That is why I can´t imagine the need for a Motif or Korg any more. Not now or within the next years. After I spent my whole life with Korg and Yamaha.

Oh yes!!! Fulfill it.
I have a Motif XS7 which I will always keep. It is the most usefull keyboard I have. But I love my old K2000 so much that I bought a PC3le before the K2 dies. The sound of a Kurzweil is for me very inspiring and working with VAST a lot of fun. Much more than the Yamaha. So for versatility Motif, for sound a Kurz.
my two cents

Well, I may add, on stage I feel much more comfortable and flexible with my PC3k6 than I ever did with my Motif. Fast access to transpose and back, drawbar-organ and well designed sounds that seem unspectacular on first glance but place themseves very good in a mix. Live and in recording. To me it´s a first class pro-grade workhorse.