I will probably give preference to Tesla and Nissan because they've both been early adopters in the BEV market.
Nissan is an early adopter in the BEV market. Nissan dealers, for the most part, are not.
This is going to be a huge reason as to why the Model 3 would blow out even a lesser priced but equally capable Leaf.
That's like saying Blackberry is the only company who have figured out how to do email push ...
When other companies have long range EVs - they will put in the money to make their charging networks widespread and reliable.
I wouldn't be so certain about that. Nissan is the only company out there with "their own" charging network--none of the others don't even have anything. And it's not really a network, because it's only in dealerships--you'll have a fun time with cross-country trips if you can only stop at dealerships to charge, while Superchargers are out along interstates.
Many companies have explicitly come forward and said they'll never build a charging network. Volkswagon is one of the more prominent companies to state this. Leaf has been quick to give out memberships to EV charging networks, but their dealer network barely has any lvl3 chargers up and running--and really, who wants to go to a dealer to charge their car? Dealers aren't always the most desirable place to wait out a 20-30 minute quick charge. I'd rather go to a shopping mall next to a Supercharger set.
What incentive is there for a third party dealer to keep their lvl3 charger up and running, versus Tesla that has real-time electronic communication when a Supercharger goes down?
The Blackberry example is great for this situation though. Other BEV manufacturers are like Blackberry, who think that their current setup will work fantastic and that it'd be OK to delay a product that people really desire. Like Blackberry, there's a great chance other BEV manufacturers will be forced into a tiny niche market because they'll be too little, too late.
I could go on about the other Tesla advantages that will likely be baked into the Model 3, such as a battery that degrades very little (huge, huge, huge--no amount of battery chemistry will make up for a lack of active temperature management), guaranteed resale values, company-run CPO program, intelligent internet-connected cars and charging network, no "model year" model to be constrained by for improvements, eight year warranty, and so on.
And finally, Tesla is an all-American company whose Model 3 will be over 90% parts sourced from America with the Gigafactory. I think that in itself is worth going for Tesla over Nissan, but that's just me. I only see hope for BEVs in niche format (REx versions, cheap city/commuter cars only) unless they give in and pay Tesla for Supercharger use and buy Tesla batteries.