For me, I guess it all boils down to how EASY any given arranger makes doing the usual tasks that you need to do to fully personalize your arranger for YOU.

How simply is it to edit and create Performances. How easy is it to edit styles, and SMF's? How easy is it to link lyric readouts with the style for that song? How easy is it to organize your data, to cover different types of gigs?

Basically, the harder any arranger makes any of these tasks, the less likely you are to actually DO IT!

I'm still an ardent Roland fan not necessarily for any technical reason, but simply because Roland make all of these tasks pretty simple, especially editing styles and SMF's, so tweaking a legacy style to use the best new sounds is not a daunting chore, but a minute or so of simply button pushing, and done! Re-working your SMF library to take advantage of newer, better kits, a snap!

It's the little things that make the biggest difference, IMO...