For price points, more expensive doesn't necessarily mean better and as you've noted, Less expensive doesn't necessarily mean cheaper. The Freilein kites are sewn better and to more exacting standards than any of the current competition. It's almost too perfect. You will not find a stitch out of place on a Feilein Kite.. If you do, OSK would probably replace it for you.
Many of the advancements or modifications on the Freilein Kites are the results of OSK's feedback for Quads they sold through the years, repairs they've made to them and the willingness to make changes to their own product based on consumer input. Those changes may not please everyone but I guarantee you that those changes were made due to consumer feedback. I made a simple phone call about the bag and they changed the bag length to accommodate..
Adjust-ability, -- once you get proficient at your normal sails, you can tweak with framing choices, bridle mods (like French bridles) and venting options. Find what's best for you!!
-Rev was the original innovator and has a very strong following and some pretty extreme loyalists..
-Freilein is a relative newcomer that's capitalizing on the expiration of Rev's patent while making changes based on their own innovations. The lower price point has gotten a lot of attention from new and experienced pilots alike.
-Phoenix is a effort by a former Rev Masterpiece Designer and producer of the B-Series Pro to provide his (Bazzer) innovations to the quad market.
There are others already on the market across the spectrum of price points and quality. There are also some very interesting designs in the "near ready for market" category. EVERYONE has an opinion as to what is best. My opinion differs from others' but I know what I like. I won't force my opinions on you. You have to individually find your options and figure out what's best for YOU. There is no ultimate wisdom and no ultimate kite. YET.