My priority is to be able to use the sounds from the manufactures I choose, not just what the Arranger manufacture makes for you. (Akai sample loading should be just a start, and VSTi can pretty much solve the rest)

Downsides of arrangers I have tried (All relate to TOTL)

Bohm: Limited styles, No Touch Screen, A little too Germanic sounding

Ketron: Small Screen size and no touch sensitivity, a lot of the sounds tend to lack body, not the easiest OS, Layout

Korg: Small Screen, Not 100% sure of the OS

Lionstracs: No practical experience, so cannot give a definitive answer (Unless you have heard or tried something live with your own style of playing, there is no way for you to really know what is like)

Orla: A bit old sounding, but a nice pleasant sound

Roland: Apart from the styles (Some of the best out there) the sound engine is way outclassed by every other manufacture (Time has not been kind to them (Now if they bought out an arranger with the new Atelier sound engine, then all other manufactures would really have to pull their finger out) small screen, heavy keybed (I prefer a lighter feel)

Wersi: (OAS 7 but without OAA with which I have minimal experience) dated styles, Re-worked voices (From previous OAS versions) not entirely successful (New voices only bettered by the new Atelier) Drum module. (The drums really are an abortion Thank goodness for Akai samples and EZ Drummer)

Yamaha: No touch screen, limited onboard control/editing, styles (Much to song specific and repetitive for me)

In the final analysis it comes down to personal opinion, so in truth there is no better or worse arranger or feature, just what suits the player.