You can set the maximum amperage in the HPWC. I am considering purchasing one, and installing it permanently, but limiting it to 10kW (I only have the single charger anyway).
It seems to be the least expensive, and most convenient (as for opening the charge port door).
I never bring my UMC with me when driving around. No real need. I do bring it on road trips (and planned charging), as well as when long term parking.
I agree completely. It's a little more money than a second UMC, but the ruggedness, connivence, and just good looks of the HPWC makes it a great choice.
Here is an idea for you single charger folks on installing an HPWC:
If you set the HPWC to the actual circuit breaker rating and only have a single charger, the car will do the correct thing and draw the 40A or pilot limit (80% of breaker, whichever is greater. See below for Table 310.15( B)( 16) from the 2014 NEC for current limits. You can do a 50A breaker circuit with a #8 Cu wire, but many use a #6 for added efficiency. If you do that with the common insulation types (center Cu column), then the wire is rated at 65A. I believe that the NEC allows you to go to the next larger, standard breaker if there is not one for your wire current limit. That would let you use a 70A breaker with #6 wire. You could then set the HPWC dip switches to 70A (56A charging). Your car would charge at 40A and have very low line loss, and if someone stopped by with dual chargers, they could charge at 56A for a 40% faster charge.