Actually, to be correct, the 980Ti is even 16% faster than the 2080Ti.
Some of you asked for a video of a render session. As there was a lot of post today, I add it here again. Real render time without screen recording and compression is around 8sec per frame with one GPU only. It uses the preprocessing option of 2.79x.
2.8x with 50% off is still available for some hours with this coupon https://gum.co/tsTuV/gumroadday, 2.79x with this coupon https://gum.co/SeYhy/gumroadday
and if you want the 2x speedup and the AI denoising node on top of a branch of your choice like Mantaflow or Fracture modifier branch, you can learn to make your own Blender here https://gum.co/ecycle/gumroadday (with 30% off today)