Section 420 truly is as good as it gets on the top level mainly because it's underneath the press box and there are no additional sections above it like the rest of the sections in the 500s. It also provides a wide view of the playing field where you are able to look down and easily follow the ball. If you sit high enough, on a clear day you might even be able to see Lake Michigan off in the distance.
These features are all very important, since the Cubs will often fall behind, let you down and you inevitably get bored. Wherever you choose to sit, note that some seats have a restricted view of the field so make sure you don't buy a seat behind a pillar. If you do get stuck behind one, you won't be able to see well, and you probably don't want to lean into the guy next to you to catch additional glimpses.

In all in all, Wrigley Field is a wonderful experience for all baseball fans, Cubs fan or not.