Well, one major difference is that you can't get a 30-06 in a Contender. Pressures are to high for that frame.
The G2 Contender is about 1.5 pounds lighter and is smaller than the Encore, but is plenty strong for the rounds it is designed for. The Encore is built to handle more powerful rifle and pistol calibers.
Until this year Contenders were the ones that you could get factory rimfire barrels for. As of this year there are factory rimfires being made for Encores, but I haven't seen one yet.
So if you have a need for an 06 then the Encore is the way to go. Be careful though. These things are addictive. I bought a Contender years ago and they seem to multiply in the safe!!