Hey Jake welcome to the forums, when I joined I was in your exact position and if it weren't for a dodgy couple who screwed me over, I would be driving a 6 MPS. There's days where I wish I had gotten the 6 over the 3 and there's also days that I'm glad to have gotten the 3. Though if I could go back I think I would still choose the 6 over the 3.
Main Reasons for me were: I just freaking love the look of the 6, where as the 3 eh so so. The 4WD while not being used at all times is still something nice to have, the 6 has a much nicer interior IMO, and well I just generally prefer the look of the 6 over the 3 though what I think you should do is take a test drive in both and decide on what you like, because at the end of the day your mainly buying the MPS to drive it, not look at it. So that would be my suggestion to you.
O and rogwick I didn't know you've never driven a 3 MPS, I'll be sure to give you my keys next time