Believe there are some HVAC experts here, so looking for a sanity check.

A while back I'd looked at the MicroAire Easy Start device for my home 5 ton heat pump. Idea being reduce start up amps so I could possibly run it on a generator, but also to make the unit start easier (quieter) and possibly prolong its life. Never got around to ordering one.

Had HVAC "checkup" today and the tech pushed a Hard Start device. He said it should bring start up amps down by 15-20, prolong the life of the compressor, and reduce start up noise (right outside a bedroom). I mentioned the Easy Start and he said they were the same thing. Of course he can't install the MicroAire one, much less does he have one on the truck.

Forgive me, but I have a hard time believing a $369 unit (EasyStart 368) is the same as a $50 unit (Rectorseal KS-1)... Or am I wrong?

you're not wrong. A hard start increases the inrush current to increase the torque to get the motor moving. it will prematurely tear down your motor. Think flooring your car every time the light turns green......that's a hard start capacitor......

They are very different. As another poster said the hard start is a momentary rush of current to get a large load moving quickly. The east start based on two minutes of research appears to be a soft start that is pulsating the voltage to the compressor allowing a lower amp draw and slower start. My concern for this is that compressors are typically starting under a good load and I'm unsure of how well it would actually work on a single phase compressor. Soft starts are commonplace in three phase equipment.
A few of the many things I've learned about hard starting compressors in my short time in the business are this: refrigerant charge and TXV can affect starting a lot, location of the breaker in panel in relation to incoming power and other high loads ahead of it can affect it, weak run capacitors are very common, adding a crankcase heater to the compressor will help. Remember on the generator that once the AC is running the load is minimal, maybe that's when your device will be worth it.

AC units have a capacitor sized to correct the power factor at the motor so that it can start easier. The compressor is a big inductor and inductance causes the current to lag the voltage. The capacitor fixes that and is sized to optimize the power delivered.

I would never change a capacitor out unless the compressor was not starting. Those things are meant to be a temporary fix for a compressor that will no longer start.