An arranger is almost ENTIRELY about the soundset. Unlike WS's, everything HAS to be available instantly, already balanced and ready to go.

This is what Dom forgot, and what anyone who wants to use software instruments for arranger use is well advised to remember. The better hardware arrangers (and that includes modern ones for as little as $1000) have soundsets that currently, no software soundset can even approach. Yes, each individual sound can be FAR better. But taken as a whole, consistency is almost non-existent. Modern arrangers can have thousands of sounds, and usually, none of them need any work before you can use them. It's hard to find a VSTi that can even do the entire Capitol GM soundset, only 128 sounds and a few kits, without major rebalancing and EQ'ing.

That's what you are paying for...