As with any component, the better the hardware, the better the product. All nVidia reference cards cards from the 1070 on up have shown thermal throttling issues, those should definitely be avoided. In previous generations, the AIB cards with better componentry and cooling showed various advantage. With the 10xx series, nVidia has put a nerf on all cards with Boost 3 capping performance to a significant extent which has reduced but not eliminated these differences which fps increases of up to 7%. As indicated above, the size of the performance differences have been reduced by the limits imposed by Boost 3 but aside from fps differences you will find significant differences in heat, noise and power draw,
Try this link and type "1080 Ti" in the filter
https://www.techpowerup.com/reviews/
Listed based up review rating, these are the ones I'd look at
9.9 https://www.techpowerup.com/reviews/Gigabyte/GTX_1080_Ti_Xtreme_Gaming/
9.8 https://www.techpowerup.com/reviews/MSI/GTX_1080_Ti_Lightning_Z/
9.7 https://www.techpowerup.com/reviews/MSI/GTX_1080_Ti_Gaming_X/
9.7 https://www.techpowerup.com/reviews/ASUS/GTX_1080_Ti_Strix_OC/
and the ones I'd avoid
9.3 https://www.techpowerup.com/reviews/NVIDIA/GeForce_GTX_1080_Ti/
9.4 https://www.techpowerup.com/reviews/EVGA/GTX_1080_Ti_SC2/
9,4 https://www.techpowerup.com/reviews/Palit/GeForce_GTX_1080_Ti_GameRock_Premium/
Performance in the OC test ranged from 206 fps for the reference and 209 for the EVGA card to 221 for the MSI (7+%). All the rest were clumped between 213 and 215