heir of Elendil can only get defender +1 while ROTN can get +3. If you face a swarm having only 1 def +1 wont be enought in that case ROTN is better. He get 4 minion and die.
(also often 2 minion is enought to overhelm aragorn).
Also, if you face 3-4 big minion you can just kill ROTN while no other damage is dealt. With heir of elendil you will assign the 2 biggest minions, he dies and you still have 1 or 2 minion left to fight.
In the end it all depend on the role Aragorn will have to play. In your case Aragorn is a born to die companion. You play it and he die soon after. So ROTN will be better.
If you have aragorn as a 4 or 5 companion and you have some healing and boost for him (possession or event) than Heir of elendil will be a slighly better choice since he will be more stable and survive longer. Since he will be able to take easily 2 minions without any exertion.
As for Captain of gondor. Giving 2 pool in the fellowship phase is huge in movie block. Plus as a support companion he is expensive and you won't use his ability much since you already have healing with
might of numenor and you will fear the +2 pool. Compare to the other 2 aragorns, he will help you the least.