I'm looking at the same two guns and also two from TC. Of the two you mentioned, I’d go with the Marlin. If you can, go and check them out at a gun shop. I thought the AR-7 felt really cheep. The two TCs are the G2 Contender or the Encore. Both of those take down fast and people rave about their accuracy and reliability. Also, you could carry an extra barrel if you wanted or needed more versatility. They are a lot more money though.
Let us know what you decide.
Good Luck.