Given how these skills don't list duration while the amount of damage absorption has been documented, it seems reasonable to assume that they may last until n damage is dealt to those protected and so the answer is that either could conceivably have a shorter duration. Bastion with the lower damage protection seems to have the shorter duration, but since it doesn't protect you, there's one fewer targets to wear it down as they get hit and so it's not entirely as straightforward as that. Duration also doesn't capture the whole picture as Bastion is very versatile because of its lower cost and enhanced usability.
There are a few key differences between Psychic Shield and Bastion beyond the criteria you mentioned. These are the ones that I found:
In this November 2011 blog post, the base values of these skills damage protection were listed as Bastion 900 and Psychic Shield 1050.
According to the wikia, defensive skills have been enhanced since then with damage scaling:
The damage prevention effect of Bastion now scales and prevents additional damage equal to your Restoration and Dominance scores combined.
The damage prevention effect of Psychic Shield now scales and prevents damage equal to 125% of both your Dominance and Restoration combined.
And on another page of said wikia, there's nothing pertinent in Bastion's description, but it does mention that Psychic Shield has a 1.4s casting time. There be some kind of a casting time advantage to be noted here, but I haven't found anything on that yet so this is interesting, but inconclusive.
Bastion is usable when controlled and costs 50% supercharge to only protects teammates, offering you versatility due to the low cost and usability when you are controlled. You can cast it twice for the same cost, yielding more bang for buck, you don't need 100% supercharge to cast it, and, if you use it when you have more than 50% supercharge, it leaves you supercharge to use for other things. I feel that this skill offers more advantages and since it doesn't encompass you, it should last as long or longer than Psychic Shield in a single cast.
Psychic Shield costs 100% supercharge to protects you and your teammates, making it simple to understand.
Which is better comes down to playstyle. If you can protect yourself without one of these defensive skills, Bastion outweighs Psychic Shield and lends itself to larger groups. Psychic shield would be more usable by a playstyle that leaves you open to attack and would fit in for smaller groups. Also, depending on whether you prefer the Illusion or Telekinesis skill trees would also affect your decision.