Two questions. No sales call. Every version does everything it does — you're only choosing how many people use it and where.
Whichever you pick, you can move up later and pay only the difference — nothing you already bought is wasted. And every purchase includes one work layer for your trade.
Most one-truck operators end up on the $299 pair, because the phone does the job and the desk does the money and you want both talking to each other. If you only ever want one of them, start there and add the other later for the difference.