Do you like Coke or Pepsi??
That's pretty much what it boils down to.
BTW, I have put together a 6 part "Basics" video tutorial series (available at the MAIW website) on FSDS which will cover most of the stuff you need to know "before" you start producing models in FSDS.
I've since started on a scenery modeling tutorial series and will eventually get to an AI aircraft video tutorial series, all for FSDS users.
Like everyone has said, FSDS is more user friendly but has less capability than Gmas or 3dsMax. So if you are a die hard FSDS user like myself, you simply learn the work arounds.
