https://wccftech.com/gigabyte-puts-an-end-to-the-horizontal-vs-vertical-mounting-debate-with-an-angled-shroud-design-concept/

In some cases, the orientation of the graphics card has caused issues. Most of the issues stem from vertical mounting choking out the airflow to the GPU since the intake of the card is too close to the side panel. Gigabyte may have come up with a potential solution in a concept design of an AORUS card with an angled shroud design posted to the AORUS Spain Twitter.

Vertically mounting a graphics card tends to be more aesthetically pleasing as it displays the fans as well as the front side of the card. Horizontal mounting is the tried and trusted way to mount a graphics card, but it isn't the most aesthetically pleasing if you aren't using a custom backplate. Horizontally mounted graphics cards show the usually plain backplate on the top and the more decorated front side with fans is facing downward. Vertical mounting is more aesthetically pleasing, but some cases don't have enough room so the fans end up having little airflow as the card gets placed too close to the side panel.