The thing with the systematic is unless you're going to mount your ball head, gimble head, etc., to the attached plate you'll have to buy the column as an accessory.
I was looking at those myself. I personally would prefer a 3 section to a 4, but to each his own,. Since, in addition to birds/wildlife, I want it for landscapes and panoramas I would likely get the leveling tripod since it has a column and wouldn't need to get a leveling base.
Series 2 Carbon 6X Leveling Tripod - 3 Section With G-Lock GT2531LVL - Leveling Tripods | Gitzo
Personally I like the height because I have lower back problems and don't want to stoop over for any length of time.
There's tons of Youtube videos out there on Gitzo - I don't see how you go wrong with it.