A "brushless DC" motor is just an AC motor, not using sinusoidal power. All EVs use sinusoidal power; square-wave or trapezoidal is just for small stuff. "Inrunner" (powered stator on the outside, PM rotor on the inside) is the normal configuration for motors; although there are few specialized EV motors which are outrunners, most outrunners are in model/RC aircraft or bike hubs. EV motors generally use rotor position sensors.So for the question, what are the up and down sides to using such a sensored brushless inrunner for a real car?
Actually, the vast majority of production EVs have permanent magnet 3-phase synchronous AC motors. Tesla was late to switch from induction to PM, but they are switching all models (yes, starting with the Model 3, but now the Model S and all coming models are PM). The best-known EV motor is the one in the Nissan Leaf, and it is a PM AC motor.From what I googled / found on youtube, the Tesla model 3 motor has permanent magnets, but not so many, and other 3 phase motors don't have any at all. What am I missing?
The Tesla Model 3 motor is a completely conventional interior permanent magnet synchronous motor, with normal size and number of magnets. Due to some bull spouted by Elon Musk, some Tesla fanatics became convinced first that it was going to a switched reluctance motor, then that it was a PM-assisted synchronous reluctance motor... but that's not true. More than one Model 3 motor has been torn down and examined, confirming the conventional IPM construction. It's a perfectly good IPM motor, though.
The only other popular choice for EV motors is 3-phase induction. That was popular a decade ago for limited-volume conversions (such as those by Azure Dynamics), that's what Tesla used before the Model 3 (and still has in some positions of some models), and there are some other recent vehicles using induction as well (such as some Audi models).
DIY conversions traditionally used brushed DC motors because that's what could be salvaged from old forklift trucks. Companies selling motors for conversions started with brushed DC motors (such as from NetGain), then 3-phase induction motors became popular (such as from HPEVS), and now the most popular choices are to salvage a PM AC motor from a wrecked production EV or to buy a PM AC motor (including from the same NetGain, who now sell the HyPer 9 in addition to their old stuff).
So, overall there are lots of up sides and few downsides to sensored brushless inrunners for real cars, so that's what most of them use. On the other hand, no one builds these motors themselves.