Hello Yves, welcome.
What is your mission? What do you plan on doing with the plane; more x-country than backcountry or more backcountry than x-country, or ???
Your questions are the type that only you can answer, so responses from the CC collective may be few if any. While I have built an EX2, I have no experience with other CC planes.
Some of your questions you may have already answered; primarily the ones on complexity and cost.
Reliability between the two engines will be determined in time.
As for 100LL not being available anymore, that is anyone's guess and the decision probably has more to do with location/country/politics.
Let us know what you decide, either plane will be a great plane.
Cheers