I too had the same debate. Just got a new frame that is both internal electronic and mechanical compatible, so it didn't have any impact on which groups I was looking at. For me it mainly came down to what felt better. After multiple extended test periods on Di2 there was nothing that was that much better about it in my mind (shifting, button/lever feel...), and in the long run I thought the shifting action felt muted: I felt like there was something lost in the process of shifting between pushing the button and having the derailleur move. The aesthetics of electronic groups isn't that big of an issue in my mind but they do sometimes have an impact on my decision. Mechanical Dura Ace and Sram just felt right. I'm not trying to say that electronic groups suck, its just that they didn't feel right/did provide enough feedback. I'm sure there are people out there who love electronic groups and I have nothing against that because that's what works for them.
Bottom line is that I went with the new Dura Ace mechanical, simply because I like the feel of a mechanical group way more than electronic. So my advice to you is test ride each a couple times and choose the one that seems like a no brainer. Why change just for the sake of changing? If you don't see anything wrong with mechanical I say stick with it. Sram really does make a great road group. It seems like to me that you already know what you want