I ride a DR-Z400 dual sport every day... litterly. I haven't driven my truck to work since November 21st, and being in Minnisota, I had some fun rides in to work. I often think about trading it in for a more dedicated Sumo, and if I find the right deal, I will.
The tire swap is 1,000, yes, but you can off set that by selling your rims and tires for 6-800, so it really isn't as bad as it seems. Though, I bet if you get it and run it, you will run dual sport for a while. If nothing else becuse I can put two full sets of 80/20 street tires on for less than the cost of a single sumo back tire.
As far as comutability, that depends on your cumute.
If you are running down the interstate for 40 minutes.... a Sumo is going to get old pretty quick. Not that it can't do it, or that it is even hard on the bike. It just isn't as nice of a ride as the SV. If you are dealing with heavy traffic, the sumo will be a god send (if your willing to bend the rules). You can buzz through traffic and find short cuts all over in a town (running train beds, blasting through parking lots, and shooting through empty lots are all options).
I have the DR-Z and my SV and ride them both a ton. If I can get there with less than 15 minutes of driving 55 or more, I take the DR-Z. Everything else, the SV gets the nod.