@Sab1e pretty much nailed it.
I:B planet generation tech is clearly better. Those planets aren’t quite the same type (for example, E:D ice planet is a Europa-type with a massive ice crust, while I:B ice planet seems to be an Iceball Earth with a rocky crust covered by surface ice).
INS doesn’t have the money to throw ground level details, alas, so it is not surprising it is lagging behind on that record.
And while more advanced, I:B planetary tech feels a bit more “immature”. For example, the rocky planet clearly needs much more work, with its overlaping craters and not much else, or the sawtooth crater rims. Even so, with no popping, a better sense of scale and a better “feel”, I:B planets clearly have the most potential at the moment.