You chose 3 marker that has different engines. It's hard to compare which marker is better. As each will have their up and downs.
Etek 4 is a poppet marker.
Etha is a hybrid poppet/spool.
Rail is a spool.
I think they all get about ~7.5 pods on a fill. So efficiency wise they are about the same.
Another question do you want a louder or a quieter marker? Etek is loud. Never heard a Etha, but i would assume its the same as the rail being its a spool. So it should be just as quiet.
Poppets will have more of a kick. Unlike spoolies, they should shoot smoother. You will have a slight kick, but its not as a bad as a poppets.
I like PE packaging better. But that has nothing to do with how a marker will behave
Go look at each of the marker specific forums, and see what issues most are having with their marker. And that should help give you a breakdown on what to expect.
If there is lots of threads about getting this upgrade or that upgrade. My preference is to stay away from those. I personally don't want to go spend 300-400 on a marker just to spend an extra 100 for upgrades. In those scenario's, you might as well purchase a used (2-4yrs old) high ends. As they will run around that price range.