A lot of people don't realize that using SMF's has changed a lot in the past few years. The majority of arranger users always pointed out that the flexibility of an arranger gave them the option to change the form of a song as needs dictate, and to make spontaneous medleys more easy to do.
Fast forward to the 21st century, and keyboards with the ability to restructure SMFs, and to either load and play them instantaneously, or even having dual sequencers to crossfade or switch between them have made many of those 20th century bottlenecks moot...
For someone with an addiction to having the most accurate style for each and every song, well, the point is, I guess, the most accurate style isn't a style at all! It's a sequenced backing
But add in the Markers ability (and some keyboards' ability to sonically revoice it on the fly, for quick orchestration changes) and you have the best of both worlds...
My needs for a keyboard are tough... I gig heavily, I play a wide variety of musics, and I play in a wide variety of musical ensembles, from the rare solo, through my regular duo with a guitarist, to full bands, to studio work. I want one keyboard to cover it all, and that is a hard job to fill!
You ask what other type of keyboard other than an arranger would you use, and my answer is, I wouldn't! In fact, I don't. BUT... my choice of arranger is very specific to the task. The G70 is by no means the best arranger on the planet (it's not the worst, though, either!), but it is FAR better than any WS at being an arranger. It is not the best WS on the planet, either, but it is not the worst either. And as a live gigging keyboard, well, there I have to give it the thumbs up
Most WS's are very poor when it comes to making a lot of patch choices and effects decisions on the fly. I guess the main thrust of their use involves setting up as much as possible in advance, rather than grabbing it on the fly. All well and good IF you have the time to do this, but if you do a lot of pick-up gigs, or like to get a little creative on the gig
having the ease of arranger operation goes a long way.
It's all about choice, and the choice of using arranger mode, or just the drum section, if you want, goes out the window the minute you change to a WS.
So what, exactly, are the WS's strengths? Why do so many use them? Here's the rub... On the whole, they are voiced and looped for VERY contemporary music. If you are doing primarily modern music, they are almost your ONLY choice, as arrangers are voiced far more 'classically' (as in 'classic' rock!). Sure, WS's have the older sounds, but apart from the vintage keyboard sound so popular now (Wurli's, Rhodes', B3's etc.) they are not really set up that well for older genres. So, probably the main consideration of your decision should be 'am I doing mostly hiphop, dance, techno, that sort of thing, or am I doing older stuff?'
You see, the main things from a WS are in the better arrangers... SMF playback, great sounds, a fair bit of flexibility, but the main thing from an arranger (the arranger!) is nowhere to be found in a WS unless you are comfortable with the 'loop' type musics. And their ability to follow chords well is primitive, compared to arrangers. Forget about fills, forget about Intros or endings (they really aren't part of that hiphop style, anyway), forget about inversions and slash bass lines...
As to the 'find the best style' addiction... well, what IS the best style? Is it the style that you have in your head, or is it the exact same style as the record, or could it be something else? I often approach my arranger as if I am playing with a bunch of real players
You know, they often have a mind of their own when it comes to how THEY want to pay a song, and sometimes it turns out that, although it isn't what YOU wanted to do with it, it is still pretty cool!
But if you are a stickler for the original groove and feel, well yes... you can spend hours trying to find the perfect style.
Or, you can make an SMF from the closest available style, and then edit the sequence until it is as close as you want it, but STILL, with Markers, be able to rearrange it on the fly. Or you can get a commercial SMF (and you still have to edit 90% of those, IMO
) and use that.
But, in a nutshell, I think that the things that you LOSE by moving to a WS outweigh the things you gain, unless very contemporary music is your main thing...
Mind you, as a Yamaha PSR user, one thing you WOULD gain would be a keyboard built better than a Costco toy!