Same engine, but upgraded components and tuning. The biggest contribution to the power increase is the larger turbos.
Lots of good info here:
https://bmwtuning.co/bmw-n63-vs-n63t...tu2-vs-n63tu3/
They're both tune happy, but the TU3 in the LCI cars is an absolute beast, and will give you the best bang for your the buck. With a stage 1, it makes F90 level power (still a very different car than the F90 though). That said, reliability is a different story, so ymmv there. Can't say it will last you longer than the TU2 in the pre-LCI cars, but it is a vast technical improvement.
If I had the choice, I'd go LCI (it's on my short list to replace the F80 next Spring), but that's just me...