ElectricMotorcycleForum.com

It was a really practical decision for me. The S is a street bike and so has street tires. If your commute includes crabby pavement or gravel then the knobbier tires of the DS will serve you more weller.
Also I agree with the lane-splitting thing. The S is fairly skinny and I can zip through traffic which is perpetually backed up whenever I'm trying to commute home. Rides beautifully in rain as well. Better than I do, in fact.
My favorite feature unique to the S is the compartment behind the battery. The DS can do the same thing should you choose to select the 7.2 which saves however many thousands of dollars and over ninety pounds.
The versatility of the DS gives you more options. The purpose-built S gives you longer range and better highway.
Also whichever one you think is cuter.

SF Moto again. Gear salesmen know their stuff, not a huge supply of stuff but w/e we just buy online anyways because who has the exact make and model of our gloves or whatever in our size?
Some of these people have been selling Zeros for as many years as they've been sold, this location is either the second- or third-closest dealer to Zero Headquarters. I had many, many questions about owning one of these things and they had nearly all the answers there were. Nearly. Also had a few floor models they sell for less.
Finance guys were killer. Stayed in touch, answered or returned my calls, replied to my emails, fought to find me a financier. Lenders don't know what the hell an electric motorcycle is so none of them want to get their feet wet but Zero found me one. Horrible jerks with worse customer service but a lender is a lender and my bank offered me a loan to buy them out at a lower rate so it all worked out.
What else... their shop repairs at a rate of $150/hr. I was there just yesterday and chatted with one of the dudes about the repair process. Scared the hell from me but since these bikes don't have a lot of moving parts repairs should be much more basic. Anyways they have guys that know how to repair these bikes and of course parts can be special ordered and installed properly.
These guys are motorcyclists, excellent salespeople and servicepeople. There's also a small kickback when you buy bikes from them. My 11k S got me about... $75 worth in a 12v low-profile socket and a dual-phone charger. Repairs are 10% off for the life of the vehicle, they've sent me a certificate for a free oil change (thank god, you have no idea how much oil Zeros quaff), free parts for my first service (since expired since I didn't total it in the first few months), and like twenty-five or so percent off a purchase. I bought a winter jacket for kinda cheap, hate every inch of it, but it's not utterly freezing so there's that. They sent me a birthday card too.
And oh yeah they have the FX, the SR, and the DS on the floor for looking and touching and they offer test rides. And when I bought mines a dude came to show me how it works'n stuff.
So yeah good dealer.