My zenith has a very nice pic but for the green cat about 1".

Besides the obvious advantage off losing the green tinge around the edges, is the image any brighter or otherwise improved by not having the resin and outer lens on the face of the screen?

Not really. Its fairly easy to remove that lens, but the green goo is nasty and time consuming to clean up. You almost need a clean room to do it in because if you get one spot of dust or hair left in there you are going to be annoyed for life at it.
Its also got to be air tight when you get it back together or it will suck dust in. You also loose some of the strength of the safety glass because its now hollow between it and the crt face.

Dont mess with it until it gets real bad.