My favourite, Terror on the Midway has a lot of restored footage I haven't seen before. Most public domain copies I've seen have a slightly altered beginning and a shorter amount of time that Superman battles the circus animals.
Like the Popeye cartoons, the colours really pop and look great. It seems just enough age was left in the restorations to keep them looking over produced, if you know what I mean.
Enough babbling! Enjoy!