Are people reading the item descriptions? RoA gains 4 AP per stack to a maximum of 40 at ten stacks. A fully stacked RoA has 100 AP, not 80.
A Difference in 20 AP and 200 HP is not Trivial. But to answer OP's Question, it kinda depends. If you complete RoA before 10 minutes, it will fully stack before 20. And since it's cheaper, You can get a head start on other items, and have a much more powerful 2nd or 3rd item spike.
The only issue with that is, RoA basically has to be the first item you complete. you don't really want to start on any other item (except maybe tier) and if you fall behind, the RoA spike will come that much later. So taking GPL works if your Really don't want to rush RoA, but still want the eternity passive and the HP boost. (As well as it's active.)