FBL systems are a very personal choice. I have seen every system under the sun on an E5 and all work well for the owners. All anyone can tell you is what their personal choices are.
I have tried a few systems over the years with most of my time being on Vbar. I never liked Ikon. The feel of the pitch was never right for me and the cyclic always seemed a little harsh, tail was great though. Vbar has a great feel on the cyclic and pitch but the tail is garbage in my opinion, but you can fly around it. CGY I have flown version 1.4 and recently started testing 2.0. I don't have too much experience with it yet but I so far I'm loving it. Right now all the settings are stock and need to do some tuning but I might be changing to it completely if my testing goes the way it has been.
No matter which system you go with, even if you stick with the same one, there are a lot of knowledgeable people in here that can help you get the best out of your E5. Let us know what we can do to help.