I have not seen any point-to-point comparison. I know that NWN 2 was buggy upon initial release, although I think they patched it. The original NWN campaign isn’t terrible, but I also don’t like the first expansions. Hordes of the Underdark is a much better game. I don’t like the earlier “premium modules” although the later ones were pretty good and there were some excellent fan-made modules for NWN. Considering you can get pretty much everything for $30, I’d probably play Hordes of the Underdark, see if you can get some of the fan-made material for post HotU, and skip most everything else.