I’d go with one bike as well, use it indoors and out, then do whatever you want with a power meter. Keep an old wheel with a trainer tire. Swap that before outdoor rides. That was my setup for a while. Easier than swapping pedals.
That said, if you stick with two bikes… I have a TT (tri) and a road bike right now, and went with dual-sided pedal-based power meter after using a PowerTap hub for a long time in training. Happy with the pedals, particularly the ability to easily swap bikes with one accurate PM, but if I had to do it again, I’d look at a swappable crank-based meter or single-sided pedals. Then again, since I’ve had dual sided power, I know my legs are well-balanced. If there’s some other reason you might have an imbalance, dual sided can have value. Otherwise, single-sided is the best value whether crank or pedal, IMO.