Sir, would you want your wife to choose a gun for you, a power tool, a car for you??? My sister's husband surprised her with a new sewing machine a few years ago - she hates that very expensive machine and it just sets there - she uses her 301... That said, I've been selling sewing machines for the last month mostly to men. I try very hard to match them up with what they say they are looking for for their wives, sisters and friends. If she does not sew at all you can't go wrong with a simple straight stitch or a machine that does straight stitch and zizzag - but make it an electric machine - if she wants a treadle or hand crank let her do it - she might get the wrong idea - like you want her to exercise more cuz you think she is fat... If she is an accomplished sewer, she might love an old well made high end sewing machine. Do some research and see what other people are saying about the machine you narrow it down to. If she learns to sew she might love one of the new electronic machines - if you already have given her a vintage machine she can still use the vintage for 99% of what she will usually sew and save on servicing an electronic machine.
BTW this topic has been discussed here
http://www.quiltingboard.com/main-f1...as-t30575.html