OP, my POV. I have both LTE and strong WiFi in my home garage. I purposely added a WiFi extender in my garage while waiting on MS delivery because of what the Owners Manual says ...but since taking delivery last October, here is my perspective:
- Firmware updates, log transmittal, use of CID Internet Browser, Media Player Streaming, and all that sorta stuff you really need to keep your Tesla going day-in-and-day-out works via cellular (LTE) connectivity.
- Firmware updates MAY be sent via WiFi, but I have never proven that to myself. It appears download of new firmware can happen via cellular data connection over an extended period of time as connectivity comes and goes. Even if you're out of range for some period, you'll eventually get any firmware updates as you come out of your parking lot tomb into range, and when all data is received, you'll get the notification that a firmware update awaits installation. There are plenty of owners that have 3G/LTE-only and have received their firmware updates.
- The Owners Manual says WiFi is required for (the much more rare Navigon) map updates, HOWEVER a number of owners reported here on TMC they received the last influx of larger map updates via LTE. It made original sense to me that large data transmittal would be done via WiFi, but it appears Tesla may not always do what it's documentation says -- IMHO, they certainly don't prioritize maintaining documentation and providing detail like others do, so with Tesla it is harder to know what to trust. I have no way of knowing how my last set of updates were delivered to my own MS, as both LTE and WiFi was available.
- It's been reported that Tesla sends "Tile Updates" as a sort of override to Navigon map data for AP-enabled vehicles as Tesla's AP Fleet learns. I've seen zero information confirming for a fact if that data is sent exclusively via LTE, WiFi, or not. Given Elon's focus on AP, and criticality of the data, we could certainly surmise LTE is used, even if WiFi is an alternative -- I just don't know that anyone here can say it for a fact.
Net of all that IMHO, is you'll be fine with just LTE. WiFi connectivity may give me a little jump on receiving some things compared to others, but it's not a showstopper or big concern to owning a Tesla. If I were you, I'd set up WiFi connectivity to where it could get it upon occasion -- just in case --, but not worry about having it on a frequent basis like say I do now.