Is there any benefit getting a 3 phase cable?
In the UK, with a Model 3, relatively modest - almost all public AC charging is either 32A single phase (7kW) or 32A three phase (22kW, but Model 3 can only use 11kW). Since the 7kW units vastly outnumber the 22kW ones, the opportunities to use it are limited and the benefit when you do only 50% faster charging.
However, if you visit the Netherlands you will find lots of 16A three-phase (11kW) units - if you use your single phase cable on one of those, you only get 3.6kW, so the three-phase cable gets you 200% faster charging (or more to the point, charging on single phase at one of those is painfully slow).
Personally, I would spring for the 3-phase cable for one to carry in the car as the cost increment is not large, but it's hard to justify unless you travel widely and expect to make a lot of use of it: I probably only use my cable a handful of times a year, and can only remember one occasion in the past several years that being three-phase made a difference (however, since I have an early Model S, it made a big difference on that occasion).
For a cable to be left plugged in to a socketed chargepoint at home, there's no point in getting the three-phase one.
