RE: which 30-30
Your girlfriend made a good choice.
Ask her why she picked the Marlin. Might give you some insight--if she gives you the same answers as you got here, marry the girl.
If she says, "It was the cheapest one in the pawn shop," marry her, because she knows how to bargain-hunt.
If she says, "I only bought it because I couldn't find a Winchester," dump her.