Gee Steve, you ask a tough question- how on earth to favour one side of such an almost perfectly balanced pair of options??

Am assuming that the IAD-SAL is on an AV narrow-body, and that likewise the COPA options are not with their new fancy lie-flat product? This would have made the choice easier.

As you probably know, the COPA lounge in PTY is dismal, so I would check out instead the SAL AV lounge instead - have not been there but found this nice review for you (a recent one):
https://liveandletsfly.com/avianca-v...ge-sal-review/