Derailleurs are somewhat of a moving target as they typically get upgraded by the manufacturer every year or so and many of the lower-end models experience trickle-down upgrades, so the X5 or Alevio of today may not be equal to the same derailleurs of just a few years ago. How do they compare to each other?
I don't know.

I've ridden plenty of older mtbs that have Alevio and Acera derailleurs and they worked just fine for everyday general riding. Shoot, my last commuter bike had Microshift derailleurs...not what I would consider great quality by any means...and they never failed me on many 50 and 100-mile rides.