One of the Team put the IV Core into a 2.1 definitely improved
The benefit of buying a 3.1 and then installing the IV Core is you can use both tips. I put the IV Core in my 3.1 and it feels very similar to a GSL now
With an IV Core, the GEO has now largely closed the key difference between with the LV1, namely efficiency. If you fine tune your LV1 it can still be more efficient than a GEO, but most players don't bother!