The RTX 2070 are not able to bridge with NVLink (lacks connector) while with RTX 2080 you can. Thou 2 x RTX2080’s price seems the same as RTX 2080TI, you will end with 16GB VRAM instead of just 11GB, so the possibilities of upgrading are better. Since it is uncertain UE will present us with multi-GPU support, other 3D software are currently able to work with multi-GPU and fine with NVLink.