my parents used one of those for 20 years until the knob broke when moving. they have gone through probably a dozen microwaves since.

Good variable power is amazing. I'm usually not in a huge rush and heating a meal over 5min rather than <1min will give you a much more evenly heated meal for no additional effort on my hand.

I also have a Panasonic inverter model. I find the pre-programmed defrost modes are too aggressive, so I prefer defrosting things more gradually by turning the power level down to 3/10 and setting the timer. Turning down the power and cooking longer are also useful for reheating thicker foods such as lasagna or casseroles so the center has more time to heat up and the edges are not overdone.

It allows for variable power levels.

That's great for defrosting, melting chocolate, etc.