Well this is an interesting question. What if you intend on having both? Personally I bought the Volt first as I was unsure about the whole electric car thing, and wanted a backup plan "just in case." Personally the Volt meets all of my needs, and I think it would meet the vast majority of everyone elses. Not to mention the car is pretty sporty looking, fast, and handles well. Not to mention for me it is kind of like an iPod on wheels for lack of better words with the touch center stack and all..
I like the Leaf too, and it has its place in the world. If you ask me I applaud Nissan for trying to keep the cost down, and still making the car very nice. In my mind GM made the Volt on par with a Buick or a Cadillac which drives the cost up. If GM had made the interior more like the Leaf it certaintly would have cut costs. I personally think both companies made the right choice for what they were trying to do.
The Leaf is simple. Granted the menu's confuse the crap out of me, but I only got to drive it for 3 days so it really was a crash course. I do like the fact that it is 100% EV. Granted the Volt is too unless it is less than 25 degrees outside, you run down the main battery, or you put it in Mountain Mode (which engages the gas motor with 14EV miles left). Believe me I have froze my behind off at 26 degrees praying for the engine to come on as I did not want to waste what little battery power I had just to create heat....
With the Volt I am not at the mercy of the oil cartels. Out of the 5038 miles currently on my car, 4348 of those are all electric. 638 of my 691 gas miles were driving the car from Jacksonville, FL to Hampton, VA. The other 53 gas miles were a few spare miles here and there where me and my wife ran over the battery mileage on our way home. Either way in 6 months it is not shabby. The last time I put gas in the car was November 8th for $3.35 a gallon at Sam's Club. Put in $16 (just over 4.5 gallons), and still have 3.6 gallons left in the tank.
So I guess the end question is why get a Leaf too since we are happy with the Volt? Personally I do not understand why it is always this car vs that car. Personally I want to shed my independance on oil too. The reality is until there is good charging infrastructure that is unrealistic. You at least need an EREV like the Volt, or a regular gas car to take on trips (or rent I suppose). While the Leaf is fantastic in town it would fall short here in Norfolk where there are only 2 charging stations (right next to each other in VA Beach). So while me and my wife can make the Leaf work here I personally do not think it would be a wise choice for the average person. Especially if they just jump in, and do not start with a car like the Volt where misjudging your range does not mean a flat bed home.
I am sure I will get hammered for these statements, but they are about as unobjective as can be. Both cars have their high and low points. Personally I like both. Otherwise I wouldn't have a Leaf on order. Is really just a shame to see the Volt get beat up day after day when it really is a great car... I do not see people complaining about spending $80,000 on an Escalade when you can buy a Tahoe for about $47,000. So for me spending $39k on the Volt is kind of a mute point. In the end the Leaf is going to run me about $33k, so it is not to far off in my mind. Just keep in mind all of you could have bought a Prius for $24k, and had a cost per mile of about $0.08/mi.. So you spent well over that to save $0.05/mi, or in some cases depending on where you live driving on electricity is more expensive than driving a Prius. Either way for those that wish to count pennies we ALL wasted money in that perspective. As the price difference between a Leaf and a Prius could easily have bought the Prius 80,000+ miles of gasoline along with paying for the car. We all have our reasons. Mine is I got tired of donating to the Middle East, and I find it convenient to have a "full tank" everyday when I leave. Not to mention the cars are powerful, and fun to drive. I know my reasons don't line up with everyone elses, but that is my 2 cents.