Although the RTX 2080 Ti performs significantly better than the 1080 Ti, I'm still drawn towards the 1080 Ti; I can buy two second-hand 1080 Ti's for the price of one new 2080 Ti, providing me the double amount of memory, plus, the computing performance of 2x 1080 Ti is much better in FP32 than one 2080 Ti.

I'm using my GPUs to train large sequence to sequence models (with long sequences) that need FP32 for training and can use FP16 for inference (mixed-precision training), so I can't even use the FP16 performance of the Tensorcores for training.

The only disadvantage is that the energy costs are higher using two 1080 Ti's compared to one 2080 Ti.