Welcome to the Synergy family. Which to build is a very hard question to answer.
I love big helis, therefore my first was a E7 and really love flying this heli, thought I'd build a E6 but was not sure to like it only due to it's smaller size, well I was wrong. Now, after over 60 flights on each I still don't know which I like best, because they both fly awesome.
I was build the E6 fly it for a week, then change it up to E7 and fly it for a week, then decide which you like best.