No matter is optimus or SLI, both ways are good as we can DIY the notebook GPU. 

If its optimus, than we can swap in any available discrete GPU in ultrabay. It save the cost of future GPU upgrading.
If its SLI, than it may bottlenet by the on board discrete GPU for future upgrade to more powerfull GPU.

Let hope that performance of ultrabay GPU are close to on board discrete gpu and Lenovo didnn't patent the ultrabay idea so that DIY notebook GPU can go to mainstream.