Most of how you will use this is related to your mechanical aptitude. There are people who should not be handed a driver license, and there are those who should not use power tools. The Flex is a prosumer level tool. If you scour the internet you will find some lively debates comparing both the units you are considering. The Flex is not as forgiving, but you can so much more in the right hands. However, you will find that some people hate the Flex, and others love it. Personally, the Flex is in a different league as I can run it run it full-bore and it never whimpers.
Decent thread to read:
PC vs Flex 3401 for Beginner?
P.S. I own a rotary too.