The answer is, of course, "It Depends"...
You knew that was coming, right?
Seriously, I expect many different answers to this question. However, this is America, and we have choices, which is good.
I'll give two answers:
For VFR with the future option of occasional "light IFR", e.g., pop through a layer of overcast, I'd go with a Dynon D100 + D120. Reasons are screen brightness, simplicity, price, and operating history:
* Screen should be brighter than other experimental EFIS. If you can't scan the screen quickly, it doesn't matter what it does.
* Simplicity - Dynon screen is uncluttered - good for a low-time pilot (me)
* Price - Less than $5k for a two screen system with engine monitoring
* Operating history - Dynon certainly hasn't been perfect, but they have been improving the same design for several years and have solved many of the bugs. I don't say "all" because one rarely fixes all the bugs in any hardware or software.
My second choice in this category would be the new ACS EFIS. Great screen size and simple display, combination EFIS + engine screens, good company, great price. GRT Sport is also a possibility.
For a robust IFR platform, I'd pick the Chelton / Direct2 system with two screens, WAAS IFR GPS module and a GRT engine monitor (which interfaces with the Cheltons). If I had the $$, I'd go for the certified / TSOed Crossbow AHRS (500GA), which has proven very reliable. Reasons:
* Good screen symbology and layout
* Excellent built-in FMS with IFR GPS approaches with HITS
* Good integration with synthetic vision, traffic (displayed in 3D), HITS
* Reliability (provided you don't have the Crossbow NAV425 AHRS)
Second choice would be a 3 screen GRT with the dual ADHRS, XM WX and WAAS GPS options, which would be about half the price of the Chelton ($15k vs over 30). Translated, this means: I'd most likely go with the GRT for budget reasons.
YMMV