Which WP8 device do you think is the best one (no matter which US carrier) overall?
It really depends on what you need. The OS and overall performance is the same on every device.
In general, Nokia is stronger with additional software like navigation systems. For everything else it depends on what you want to do with your phone.
The 1020 takes better picture than the 925, the 925 takes better pictures than the 920. However the 920 and 1020 are big and heavy, the 925 is expensive for it having basically the same hardware as the 920. If you want to play games you'll have to take one with 1 GB of RAM. Additionally you should think about how much internal storage you'll need.
I would recommend you to go to some stores and just see what fits you best in terms of size, design and price.
Personally I own a HTC 8X and I am very happy with it.