As I understand it, the sub-LR Model 3s are limited to 32A with any L2 EVSE. (Some L2 EVSEs provide less than that, in which case the Model 3 adjusts its charge rate down to match.) You can wire Tesla's Wall Connector to a circuit that permits faster charge rates, but your car simply won't take advantage of the extra speed. It'll be there in the EVSE, though, so it might become useful if you trade in your Model 3 for another one or if a friend or relative visits with a Tesla that can charge at a higher rate. Personally, I wouldn't pay a lot for more capacity, but if it's just a few bucks, you might as well do it. (The big cost driver will be in the wiring from the EVSE to your house's breaker box, which has to be thicker, and therefore more expensive, for a higher-amperage line.) Even a Model X with the biggest battery will charge fast enough on 32A for most peoples' needs.
More broadly, a Wall Connector has a number of advantages over Tesla's Mobile Connector:
- Higher amperage -- As above, this won't be a big deal for you now, but might be a modest benefit in the future or on occasion if you have visitors who drive Teslas.
- Better weather resistance -- If your installation is outdoors, I'd go for the Wall Connector because it's likely to be safer when used in rain or snow. This isn't to say that a Mobile Connector is a death trap or anything; but there will be at least two extra plugs involved (at the NEMA 14-50, or whatever wall outlet you use, and on the EVSE itself). Tesla doesn't make it explicit, but I'm guessing their Wall Connector has at least a NEMA 3R weather-resistance rating. I have no idea if the Mobile Connector has such a rating at all. Of course, if you'll be keeping this equipment in your garage, this point is, well, pointless.
- Better theft resistance -- The Mobile Connector is easily unplugged and stolen, if it's in a public space. You could build or add a locked box in which to keep it, but that adds cost and complexity. Again, this factor is mostly important for outdoor installations, not if you'll be using a garage.
- Better cable management -- The Wall Connector includes a built-in holster, and it's available in two cable lengths -- 8.5-foot and 24-foot. The Mobile Connector has no holster and is available only with a 20-foot cable. Thus, the Wall Connector may make it easier to manage the cable and/or to have it reach your car's charge port. Details vary with your specific circumstances, though. If your breaker box is in your garage right next to where your car's charge port will be, for instance, you can buy the version with the 8.5-foot cable to simplify cable management and install it next to the breaker box to minimize installation costs; but if the outlet or EVSE would have to be far from the car's charge port, the version with the 24-foot cable might be preferable.
- Convenience/Backup -- If you buy a Wall Connector, or even a second Mobile Connector, then you can keep the one that came with your car in your car at all times, with minimal fuss. If all you've got is the one Mobile Connector, then you'll either be driving around without an EVSE in the car or you'll need to move it between storage in the car and use plugged-in state whenever you want to drive vs. charge. Having the EVSE with you isn't necessary, but the EVSE can be a backup/emergency charge solution -- say, if you forget to charge or if you have a problem charging for some reason (an extended power outage, maybe).
- Redundancy -- If you have two EVSEs, then a failure of one means you'll still be able to charge.
Overall, if you have a garage, then the reasons for getting a Wall Connector are slim, but not non-existent. If you charge outdoors, though, I would recommend getting a Wall Connector (or conceivably a third-party J1772 EVSE, if you expect to be charging non-Tesla EVs any time soon).
Of course. If nothing else, the old wiring could be pulled and new wiring put in for whatever EVSE you want. I don't see why the existing wiring couldn't be re-used, although the fact that it's already cut to length means you'll be limited in options for where to mount a future EVSE. You might want to discuss this with your electrician, to have the install done in a way to maximize your options. One more point: Many wall-mounted EVSEs are available with NEMA 14-50 plugs, so you may be able to use one that's so configured, rather than hard-wired. I vaguely recall seeing something to the effect that Tesla once sold a Wall Connector variant with a plug, but it's not currently on their Web site. I have no idea what the odds are of Tesla adding that configuration back. Adding a plug to one that comes with a hard-wiring "pigtail" should also be possible. Again, that's something you might want to discuss with an electrician.