the best community site for info on Kurzweil is www.sonikmatter.com. i'd lurk for a while before posting -- although they're quite knowledgeable, some of the guys are real jerks and not nearly as friendly as the folks on this site.
i prefer the Kurz for it's orchestral sounds and pads. something about VAST gives you "that TV/Movie sound". that said, i'm really enjoying my Fantom-S because it's got a lot of nice modern features -- drum machine pads, a zillion onboard sounds, USB, memory card, yada yada. I also have a Triton Rack, but it's a recent purchase so I cannot talk much about it strengths (atmospheric pads) and weaknesses (the WORST pianos) in much depth. anyway, most of y'all will agree that each vendor's products sound a little different than the others, and it's always preferable to have a wider/deeper palette of sounds than a thinner/shallower one.
one cannot compare the true 48 simultaneous voices on the Kurzweil line directly with the purported larger polyphony of the Fantom, Triton, and Motif, each of which may lose polyphony when sounds are stacked atop one another. the VAST architecture includes a great dynamic allocation scheme which makes it work as if the kurzweil has more available voices. yep, it's simultaneous NOTES, not OSCILLATORS, because VAST is a completely digital system that EMULATES how digital or analog synths produce and manipulate sound. There's even a dude who figured out how to get VAST to produce FM tones like the DX7, whereby source audio is modulated by an "operator".
there's been an awful lot of debate about the future of kurzweil. they have been owned for several years by young chang, who were recently bought out by samick. the new management has dropped a lot of staff and it's quite possible that kurzweil will be sold off or possibly even just scrapped outright... making the $3600 purchase of a K2600XS sting just a little more than usual. the K2661 is a bit more modern and cheaper than the K2500/K2600 models, but if you don't need to move your keyboards to gigs, I'd look for a used/b-stock K2600X or XS with the 88 weighted keys and ribbon controller. The kurzweil X series are perhaps the most expressive controllers EVER built, as they have pitch & mod wheels, *2* ribbon controllers, and multiple buttons and sliders for modifying settings while you're playing... plus an input for a breath controller. roland/yamaha/korg never quite "got it" in that department, and have instead focused on making cheaper, lighter keyboards that aren't so bad for your back OR bank account. patch selection is MUCH FASTER on a kurzweil (or XV88 for that matter) because you can type the corresponding patch number (955+enter -- "BATMAN STRINGS", my favorite patch) *way* faster than spinning the alpha dial a zillion times on your fantom to get from User 1 to SRX4. Sure, you can save favorites on a Fantom -- that's a feature Kurzweil had back in '95. (this would be my pet peeve -- why can't roland hack the fantom OS to let us use the drumpads to select patches?)
kurzweils are like british jaguars -- very expensive to own and maintain, but "worth it" to a certain customer. they were a decade ahead of everyone from 1990-1995, but since then, the Japanese companies have caught up and in many ways surpassed them. here are some examples: my K2500XS has an onboard 2gb scsi hard drive (more than a motif/triton/fantom) and 128mb ram (less), 2 external scsi connections (more), a floppy drive (antiquated), and KDFX, a $700 add-on effects system that runs on additional DSPs not found in the original model. KDFX is bundled for free on K2600's including the K2661. the $300 ROMs for contemporary and orchestral sound good, but with Roland you get a TON more patches (100 vs 300+) with every $220 SRX board. the KDFX Leslie emulation blows away the leslie effects on the fantom, and since the fantom lacks a mod wheel, I can't just "dial up" a leslie setting and play 2 fisted chords -- instead I've got to rest my left hand on the joystick which has a tendency to sound more like "LFOs gone wild" than "Greg Rolie was my hero". thank goodness for my VK8
now to answer your initial question: can a fantom be used to make good-sounding commercials and tv/movie soundtracks? absolutely. BUT, I find the Roland sounds to be a little more "hyped" for pop music production, while the Kurzweil tends to sound a little more dark. i like them both, and play them to their strengths.
of course, if you have any further questions re: kurzweil, feel free to ask away.
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