While I have no personal experience with the G2, other than checking one out in a store, the one I handled did almost "fall open", which neither of old frames will do. Not even close. In fact, it takes a good hard squeeze to open them. Not a problem, just something you need to get used to.
On those ocassions where I have had others shoot them, and mention how hard they were to open, I just say, "Grow stronger!"
The G2 will recock without opening the action, something which never seemed to be much of a concern to me.
While the one I handled was pretty good, I have heard reports from several people that the G2 trigger is not as good as the old Contender. It may be true, but I think that you should check each individual gun, as they can vary, you know.
The G2 is also said to be able to use all the old Contender barrels. That's a plus, in my book.
The Encore is bigger, and beefier built, so it will handle large rifle rounds. Myself, I never saw the advantage of that, in a handgun. Now, for a light single shot rifle, thats another story.
One thing about choosing the Encore, pistol caliber barrels are scarce on the ground. The are supposed to be available, and almost certainly are, on order, but I never find them at shows, or in shops. Rifle calibers abound, but no pistol ones for the Encore. And, Encore barrels do not fit the Contender (any version) nor vice versa.
The "advantage" to buying an old Contender is that they are pretty damn good guns, and used prices generally run less than new retail. In my neck of the woods, $450ish +/- is a fair deal for a frame and barrel together. I have bought a number of used barrels for $125-225, depending on details. Prices on everything have been going up, and so things are likely to be a bit higher next time I go barrel shopping.