The Wersi should give you all that you need, but as GJ says they are expensive, but in the long term work out cheaper due to their upgradeability.
Also remember that if you have bought 2 TOTL Arrangers to help get you what you want, then you will have paid as much (And possibly more) then a Wersi Arranger, which still has more features then the other 2 combined.
A good way to look at it is:
Do you like changing your boards every so often to get new features or would you like to get the same new features without changing your board.
Both do the same job, but software updates (Wersi) work out cheaper.
Whatever you decide it will be a personal choice, as there is as yet (And unlikely to be in the future) no perfect Arranger Board.
BTW the Wersi can now also directly play Yamaha styles (No conversion required) and adds the life back into them that the Yamaha sound system removes.
Also consider Bohm, as these are hardware updatable.
Happy decision making

Bill