If you are really going to purchase the car as a 14yr car (I think this is unrealistic these days with the way tech is moving), I would be hesitant to buy a Volt. A full electric with big range and future looking options like DC fast charging is the way to go. The Tesla Model 3 is only car on the horizon that fits this criteria IMHO. The Bolt is great now but lacks serious DC fast charging (only 50kw), and GM hasn't had a good record on providing long term upgrades (or even short term). Tesla seems to be the only car company that has offered after sale upgrades (continous software updates, and the battery pack upgrade for the roadster or unlocking options after the fact like larger battery or supercharging). The Volt is a great car but I think you would be kicking yourself 5-8years in because it will never be better than the day you bought it. (unless some awesome aftermarket battery upgrades appear, 30kwhr would be amazing!).
I leased my 2017 (first lease of my life), I did it for a variety of reasons, but one was to limit the amount of technological lock in that long term finances ensures. The other was here in Ontario you still get the full $14,000 rebate on a 3yr lease (and lose less of it too tax on a lease), my employer was also willing to up my car allowance for a plug in car to offset company full costs savings.
I can still buy out my lease at the end for $14,000 after 3yrs so if tech moves slower than I anticipate I will likely buy it and drive it another 3-5years.
But, from a pure financial perspective financing/cash purchase is likely the best option. Cars are almost never an investment just a carefully planed divestment. So just decide if the leasing TCO matches your financial goals.
The state of car tech is moving faster now than it ever moved in the 80's, 90's or early 2000's. Back then 15 years in a car was not that painful (my parents just got rid of the daily driver 1997 Chevy suburban a year ago, it treated them well with over 500,000km).