Spalding, I have to confess too that I'm only an occasional user of the full arranger section, maybe 30% or less of what I perform. 30% I use SMFs, and 40% I play LH bass and just use the arranger's drums.
But the reason I use an arranger instead of the workstation is that for the few times I DO need it, it is there. Particularly seanbaker's PA1XPro, this has almost a complete Triton engine, sample import etc., and has what I would consider the most workstation-like synth engine and editing capabilities.
So, very few compromises compared to an equivalent workstation, with the arranger engine FOR WHEN YOU NEED IT. However seldom that may be, it is still FAR better than any workstation's arranger capabilities.
I also am beginning to find, with most of the current TOTL arrangers, that setting up performance setups on the fly is FAR faster and easier than most workstations. I have Kurzweils and Tritons, and have used many others in the past. If I had to go out on a 'call' gig, no preparation, not knowing what I will need to play when I get there, I will take my G70 over ANY other workstation in a heartbeat.
The ease of setting up sounds, splits and layers, effects, balances, touch response, etc., etc., on the fly are of enormous importance. If I've got a week to prepare, that's MAYBE another story, but if I've got to do it NOW, I'll take the G70, thank you very much.
I feel that there are MANY good reasons to use an arranger, even if NOT for the arranger section....!
_________________________
An arranger is just a tool. What matters is what you build with it..!