Arrangers today are just as good as workstations.

The sounds are just about on par with workstations. And if you are not satisfied the high-end arrangers come with a sampler and sound editing capabilities just like workstations.

Regarding styles on an arranger, I think whether you use the on board styles or create your own does not determine if you are a professional or real musician. The quality of your work and the seriousness to which you take music are more important to me. If the final result is something that people will enjoy, styles or no styles that is more important to me.

Also one good thing about arrangers is that on most of them styles can be created. If you are not satisfied with the factory styles, you can make your own to suit your playing or original composition. Better yet on the new Korg arranger, you can totally replace all the factory styles with your own.

If styles are use to form the base of a song, why should that be looked on as a less professional thing than using factory arpeggiaters on workstations. One of the things with today’s music and hits, factory made drum loops and other instrument samples are being used and tweak to be part of a song. So why not styles?

But for composition today, it is always good to have different instruments sources.

If you are a solo act, a band keyboard player, and a composer I think an arranger is the most versatile way to go. You will have the style function for a solo gig, and for composition a sequencer, sampler and sound editor all in one if you get the right arranger. Not to mention it is the most economical way to go.
If you have a chance try to take a look at the top end arrangers and what they can do.

But regardless of what you get to make or play music, the professionalism/realness and seriousness of a musician and the quality of the work really depends on the individual making and playing the music and not on the type of equipment being used.