According to documentation we should use ETC2 texture compression for deploying to Gear VR.
However, all Gear VR compatible Samsung phones support ASTC which is way better than ETC2 (both size and quality).
Are there any considerations to prefer inferior ETC2 over modern ASTC (honestly, I don’t see any)?
According to this forum post, you should use ETC2 when creating a project in UE4 even though Oculus recommends ASTC. Obviously you are more than welcome to try out both and see what happens, if the results are good/better than expected, post something on the forums, make a big stink about it. If it’s that good, people should know and the recommendations may change. Maybe not, but it doesn’t hurt to try.