I just completed a panel upgrade in my RV-7 two years ago, and went through the same mental anguish. I spent the better part of Oshkosh 2016 parked in front of the Dynon/Advanced booth just pushing buttons, asking questions, examining user interfaces, and generally making a nuisance of myself.
Two things I really liked about the Advanced is the ability to have the EFIS control a remote audio panel (saves space in the radio rack) and the user friendly NAV modes for IFR.
I finally decided to go with the Dynon panel. I liked the menu system - it just seemed intuitive and easy to navigate. The Dynon system works very nicely in an IFR environment. My CFII (who got his first taste of glass IFR) was extremely impressed with the information that I had available on the Dynon, including HSI and artificial horizon overlaid on the PFD, while also having IFR charts or approach plates visible at the same time, and having my aircraft location following on the chart or approach plate.
I'm building an RV-14 now, and plan to put in the exact same panel as my RV-7, but upgrading to the HDX.