Open air 2080ti's will dump hot air into the case and make the vrm cpu and ram 20-25c higher. Temps on the actual gpu will be exactly the same as the blower, however it will be more silent while cooling itself.

Blower will avoid that 25c penalty on the cpu vrm and ram, but will be noisier cooling itself.

If this wasn't a Dan A4 but instead a bigger case, the open gpu would be more silent AND cooler, rather than just more silent, as for the temps in the case it would be less than 20c added on to other components, and it could be brought down to as low as 5c with proper case fan placement and speeds.

The above is the reason Dan recommends blowers, unless your using a 65w cpu, at which point the 25c added won't affect it (make it throttle).

If you have any more questions ask.