Check your local code about running the wires in conduit. I'm getting a new 14-50 socket installed, and in researching where to put it, the electrician noted that if we locate it in a place where part of the run is in conduit (most is simply under the house), we'd need to strip off the outer sheath of the Romex first - just run the individual (insulated!) wires through the conduit by themselves. I'm guessing this is to prevent the build-up of excessive heat.
My 50-amp circuit (40 amp charging) could run #6 wire, but I chose to use "#4/3 with ground" to give some headroom, and to reduce the voltage drop. The run is just under 40 feet end-to-end. Given the cost to run wires, I'd pull the most you can afford. My Roadster can charge at 70 amps, but my EVSE can't supply that much, so we're doing just the 50 amp circuit now, with the knowledge that a simple breaker change and a new EVSE in the garage could enable the higher rate if I should need it in the future. I'm also adding a pair of dedicated 20 amp 120v GFI sockets by pulling a length of 12/3 as well. If nothing else, it would provide a convenient backup socket near the car in the event the EVSE goes bad.
I believe you are correct that most EVSEs don't use the neutral line, just the two hots and ground. Depending on what form your wires are (individual strands, or bundled as Romex), including the neutral line may not cost much if anything. Again, it could be cheaper to pull it now, than trying to add it later.
