ACER fixed there issues? You need to look again, go look at reviews, they are still terrible. The ACER Predator X34 still have QC issues, the ACER XB271HU has not been out for long.
If you look online again, you will find ASUS fixed most of the issues with the PG278Q, however the PG279Q is not fixed, due to AU Optronics.
Start looking at customer reviews.
Samsung should release a panel by the end of next year (I expect with Freesync) which has better QC than ACER and ASUS.