We have both the Volt and the Leaf. We have about 4100 miles on our Volt which came on January 13 and 2500 on our Leaf which arrived at our home on 17 February.
The Volt is fully functional as one's single car for all purposes; the Leaf is an around town commuter...period. Even with DC charging, when it comes available (we did get the QC port @ $700), it would still be a pain to stop for 30 minutes just to get another 70 miles range or so.
Hence for real use, be sure you recognize that the Leaf, at least in our experience and even after the recent software update, is still range challenged and the range display is absurdly optimistic at initial full charge. We still see range displays around 115 miles when we leave our garage and in the first 10 miles LOSE 30 miles on that display !!!
Our Volt range display has never been off by more than 1 mile and it is usually conservative. We see 40 miles EV range upon leaving home and find that after driving 25 miles we have 17-18 miles range remaining. We have regularly gotten as much or more actual EV range as the initial display even when we drive fully into ICE operation.
The lease program is the way to go on the Volt, IMHO, and our almost fully loaded Volt (we did NOT get the fancy wheels, but leather, backup camera and mats) is only $30/month more than the Leaf lease and it was $1000 more to initiate the Volt lease. The seat heaters on the Volt make my wife MUCH happier than the horribly weak heater in the Leaf, and the Volt does have height adjustable seating with a range that truly fits a short driver (she is 5'2").
We like both cars and enjoy the complete EV operation of the Leaf, but the Volt is a more "fun drive" and a much better sorted out electronics package. The GPS system in the Volt has maps that are much more up to date than the Leaf's (our neighborhood streets are not shown at all on the Leaf GPS, and this area has been populated for 5 years or so...). The Volt comes with a real "cell phone" built in and 100 minutes in the first year of free calling. OnStar is amazing and free for 3 years with the Volt. The Bose sound system in the Volt makes the Leaf stereo sound like it came from the 1950's.
The Volt LACKS proximity locking/unlocking (a total pain-in-the-***) and it should have a rear window wiper (both are standard on the Leaf). Is the Volt "worth" $10K more than the Leaf? I really don't think so either, but I do believe it is a much better total package than the Leaf, more indulgent, and more well-designed. The traffic warning/XM/Sirius radio system in the Volt is MUCH more informative than how that system works in the Leaf.....and all of the electronic displays and driver feedback systems work better with more actual information than what is provided in the Leaf. Again $10K more? Probably no, but for commutes of under 40 miles, when both cars are sitting in the garage, I chose the Volt every time.