Well, for my money I go for Yamaha because of XG. If you don't know about that, it's Yamaha's extension to MIDI. With instrument banks and sysex my arranger turns into a workstation as well (needs a computer to drive it though, but they're cheap enough these days). Yamaha is very popular in Europe - just look at the styles on an arranger and you'll see why - it's their second biggest market after Japan.