welcome Mr Smith!
The RRA products are very good and many here rave about their quality and durability
as far as which one, I believe cvg covered that well, but with regard to the on-line buying/FFL thing...........
Piece of cake.
you go to your local FFL (after selecting a dependable and economical one. Some charge as little as $10 to handle a transfer, and others as much as $50 or 10% of the firearm value, whichever is greater. So their is a difference.)
He will give you a copy of his license and you can either mail it or fax a legible copy of it to your firearm dealer.
Pay for the rifle.
and when it arrives at your FFL location, you do your forms and blast away. (notwithstanding your state's laws regarding wait times, etc.)
Unless the seller is within your home state, you do not pay sales tax, which often is a substantial savings.
on a side note, have you looked at Bushmaster or Colt? Both have great AR products and are in the same general price range as RRA.
just a thought.