Screen size, resolution, the APU, storage size, controller connector, buttons, the lot. They did state that they worked on the stick drift issue and found ways to mitigate it, but they weren't specific unfortunately.

To name a few things, they improved the processing power, storage, screen, attachment method of the joycons, dock, placement of charging cable (located both top and bottom), in-game chat.

I'm not going to buy one cause the pricepoint and the fact that "physical copies" of games are going to be empty cases with keys, which might be able to be lent or resold until Nintendo decides against it or kills the system for verifying them, but they did make a number of improvements that would have opened up my wallet once again if they hadn't let greed win the day.