It's the little things that make the difference between a Gitzo and the knock-offs. Gitzo uses quality materials and the others usually use a lesser grade, slight differences here and there that may not show up for years. Glue in these joints vs bolted or clamped, magnesium vs cast aluminum, steel inserts in high stress areas vs native metal, stainless steel hardware vs steel, less dense carbon fiber vs more dense, lesser aluminum alloy vs better alloy. My background is an aircraft mechanic and pilot. I want quality, I crave quality, I recognize quality, I can't afford not to, my life or the lives of others literally depend on it.
I've owned a Manfrotto, Benro, Slik, and Gitzo. I've used Feisol, and Velbon. For sturdiness, and top notch construction, the Gitzo wins hands down. I was actually amazed when I stepped up and spent the money. Of course I went from a Manfrotto 3221 to a Gitzo 1410 (lighter weight Benro travel in between) and even though the Manfrotto is a good legset the Gitzo was several steps above. My Benro just doesn't have the damping the Manfrotto or Gitzo have, the slightest vibration is translated with the Benro, where the Gitzo and Manfrotto are absolutely solid and damp out almost immediately. Subtle differences and differences you may never notice. My biggest knock on the Manfrotto is having to bend over all of the time, it's just a bit short.
With you using the tripod as a car tripod you really have no need for CF, a good Aluminum Gitzo will save you about half in the price of the legset. The Gitzo 1410 (Adorama has a used one for $299 right now) is the next incarnation of the legset Art Morris uses for his BIF shots. You'll never go wrong with a Gitzo 410(1410) for a long lens with a Wimberley head for birds. It's a big heavy rig, but that's the point isn't it. I have a hard time putting a Mark II plus 500 f/4 ($8500) on much less.
Rule books are paper they will not cushion a sudden meeting of stone and metal -ekg-