I think the reason why he scrapped the Unity version is that it was just SO buggy and broken in so many different ways. That it would have been both way harder and more work to try and fix it than it would be to start over. Not to mention the unity version wasn't even that far in the story IIRC.
As for going for full 3d models and animations while they are harder to make initally, the upside is that once made you can do whatever with it. You don't need to make another for new animations etc. So if he has the skills to make a 3d model then it might be faster. Especially if multiple characters share a similar base look.
One other upside is we won't have the weird massive heads anymore on the models. And if it stays first person well we will actually know where we can go instead of getting stuck on invisible walls... Hopefully.
