The LEAF has been mostly outselling the Volt since the 2013 US built model came out. LEAF would have outsold the Volt in 2013 had it not been for very poor LEAF sales in January and February before the US transition.
I think it comes down to commitment. Nissan has kept doubling down on EVs. They are rolling out charge stations to all their dealerships, giving out quick chargers. They've been promoting fairly heavily and effectively. They've been offering exceptional lease deals. They've publicly stated that they're serious about EVs and expect to do more.
Contrast that with GM. They've had a very strange inventory management philosophy that looks like desperation. Each year they way over build in the spring, stop building over the summer, then have a flash sale of desperation in the fall and announce a new model year with no real changes. Smells of desperation. Of a company not proud of their car but having to sell off inventory.
Ackerman's comments could have been positive, about GM's commitment to EVs and future enhancements. Instead it came across as todays car is way over priced, we're reluctantly selling them at a big loss. They're going to be a ton cheaper and better in the future so why buy now?
ELR has been a disaster. Embarrassing that GM thought they could compete with Tesla by simply doubling the price, making the interior fancy without improving the fundamental mechanics, i.e. battery capacity, performance, etc. Then insult the world and their EV core with a pro-American, anti-world, anti-green advertising campaign.
GM has not rolled out EV charging stations. Charging stations that may be present at Chevy dealerships are not public, not available for charging.
GM has pushed CCS, the combo charging solution, trying to slow or stop chademo while not lifting a finger to deploy CCS. Typical FUD and stall.
Overall, bottom line, looks like Nissan is trying hard to lead in EVs.
GM acts reluctant, uncertain, uncommitted.
Besides that, I think the Volt is not a comfortably sized car. They need a car with better use of interior space. Having the battery in the cabin may have worked for the EV1 but not in today's car. They need to move the battery out of the way, support 5 passenger seating, have a taller more spacious cabin with better visibility.
The LEAF is far from perfect, can be bland or distasteful styling. But its a generally competent, comfortable car that can appeal to a broad segment of the population world wide.
And I still wonder if the whole idea of a PHEV is fundamentally flawed. You end up with the worst of both worlds. Have to carry around two complete drive trains. Neither can be as good as a car with one purpose built drive train. Carrying around both a complete ICE and EV drive train causes extra weight to be carried around all the time, less performance, less interior space available, more cost. The other PHEVs are more like hybrids with a small battery. I think its very possible that as batteries come down in price, BEVs with better range will win out over a PHEV. You could argue they already have.