To D3 or D4 that is the question.

Hey everyone - need some help choosing between two D's! I've spotted a D3 and D4, both 2014s with about the same miles on them. They're miles away from me so I'll pretty much need to decide which one I want before I make the journey to see it. I'm keen on both of them, and since it's just going to be me using it for my motorway commute, the D4's lack of back doors isn't an issue. Anyone driven / owned them both or got any tips to help me pick between them?