Several years ago, I flew with an FO who had come to EK from Copa. I asked him if he felt more fatigued/tired there than at EK. He actually said Copa.
I later saw a captain's bid sheet from there and it was much like EK's. 9 days off and only 2 in a row max days off for the bid I saw. It looked pretty busy to say the least.
It was my opinion at that time, that to go to Copa would be the proverbial frying pan to the fire.
The only thing IMO better there was it was only 2 hours max time zone changes for all flights. Some all night stuff, but not nearly as much as EK does.
Kap