We are sort of discussing the differences (and similarities) between arrangers and workstations, it seems to me. Or are you asking what makes a 'good' arranger? Genesys, you're first few lines of your post seem more in that vein...

Firstly, let me say that NO-ONE has accused the MS of not being an arranger... Just not a good one (yet). An arranger is the combination of hardware, software, and CONTENT.

This is one of the major differences (in the past) between arrangers and workstations. Workstations were sold without content. Until the Triton (I think, not sure about the first one) there were no loops, pre-recorded arps, or full sequences that came with a workstation (WS). You bought it strictly for the sounds and features.

Arrangers, OTOH, have ALWAYS been about content, as well as sounds and features. No manufacturer ever sold an empty arranger and said 'OK, here you are. Make your own content'. They gave us (eventually) the ability to add more content, and finally even make our own, but never attempted to make us do all the work first. The skills required to make an entire style library, at anything approaching the level of ROM styles is completely beyond most players. Even the majors now use a team of programmers, with drummers playing pads, MIDI guitarists and bassists, and skilled imitative keyboard players.

It is no secret that many (dare I say most?) workstation users don't always do their own sequences, relying on third party SMFs to get that 'full band' sound, or at least drum and MIDI guitar libraries to get those tricky parts authentically. That is, if they are using it as a 'virtual' band or rhythm section. Studio use is another thing.

This is one of the 'problems' (I say advantages!) of todays TOTL keyboards. They do everything! You can use an arranger as a workstation, and you can use a workstation (especially the MotifXS) as an arranger. But how well do they do each task? A LOT depends on the type of music you are trying to perform.

For simple loop based hiphop, techno and urban styles, something like the MotifXS would be all an arranger player would need, with little need for Intros and Outros, Fills, Rit/Accels etc., but, as is being realized, for more complex musics, not quite sufficient to do the job.

I think the Keyboard article nailed it with the analogy of a workstation being a situation where you say to the drummer 'OK, play kick on 1 and 3, syncopate your hi-hats and play the back-beat on a 12" brass snare, bassist, play an upright bass, swing it a 63% and play these notes' etc., etc.. And an arranger is you in charge of a band and say 'OK, let's play this one like KC and the Sunshine Band, key of Bb, 1-2-3-4....'

How much you need either of these approaches depends a lot on where and what you are playing, and with whom...

There is no doubt that most of the TOTL arrangers double as an extremely good live band keyboard (in fact, I prefer them to most workstations because of the more 'meat and potatoes' sound sets, and intuitive splitting and layering and effects options compared to WS's). Let's face it, an arranger is designed from the ground up to be used 'live', and most WS's are designed more for studio flexibility than live ease. But if you are in a full band, well rehearsed, then the flexibility of the WS may be of more value. This one is a tie (IMO).

But an arranger, WITHOUT good styles is a crippled tool. IF... you are using it as an arranger. Use it as a WS, and cool, no problem. Use it as a live keyboard, cool, no problem. But if you want to use it as an arranger, for the purpose that arrangers are PRIMARILY designed for, the styles are probably more important than any other feature. Great styles with a less than average sound set go a LOT further than great sounds with a less than average style selection.

If you use your arranger for what it is primarily designed for, rather than as a vague hybrid, then yes, the styles are almost the ONLY consideration. If you need marginal style functions, but extensive WS functions, then MotifXS's and MS's may fit the bill.