I own an Inspiration and I am Inspiration instructor as well. I also own a sidekick and have for 9 different ccr brands a user level.
I have dived my Inspiration up to 135m depth, done dives of 6 hours, so it works for me. I prefer on some narrow caves the sidekick, but the WOB is bad if you know how it can be on an Inspiration or JJ.
I don't feel any differences between the JJ and the Inspiration, but I have seen that the alu scrubber pot of the JJ was deformed after being in a plane, something that is almost impossible with the Inspiration.
I do not like the bulkyness of the Megalodon. And also the XCCR is very heavy to travel with. It dives ok.
Also the Poseidon dives ok, but I hate all that automatic tests before you can jump in the water and if you are too slow, then the computer has turned off and you have to climb on board again to do all the tests again before you can dive. This was very annoying with this machine.
The prism2 dives ok, but the quality of the lungs feels like it is cheap thin material.
I have used the Evolution/EVP on my ccr instructor course in Florida when I did not bring my complete unit, only the electronics. And also that smaller machine dove ok and I am 1.82m, so quite tall.
If I have a question about an Inspiration, an email is answered most times the same day. If you call them you get the answer directly. If you sent files from the unit to them to analyse, they will do.
So for me no need to change to another brand and even if my unit is from 2009, it is completely supported (not like Megalodon did after 10 years), and I can buy all upgrades, spares, etc. I have the 2020 handset as upgrade. But the first stages are still the same, never replaced, only serviced sometimes. I also upgraded to BMCL, but the FMCL's were not bad, only bulky.