AFAIK, there isn't much difference between the two, as far as the action goes.
The #1 has a lever lock and the #3 doesn't. Also, I read that the #3 never had an adjustable trigger, but current production #1's don't really, either.
The forends both attach to a spring hanger, though the #3 has an aluminum barrel band for cosmetic purposes.
As far as caliber goes, I'm kind of partial to the .30-06, but the choice does depend on what you intend to do with the rifle. I only have two, one in .243 and the other in .30-06.
However, I understand some people
collect these things...
