I've used both, and I find twist locks faster and easier. A whole set of twist locks can be easily loosened or tightened with one hand. A set of flips can be closed with one hand, it's harder to open the whole set. With most flip locks, you need a tool to disassemble the legs, not needed with twist locks (important if you use the tripod in water/silt/sand). Twist locks allow you to loosen a leg with some tension, making height adjustments easier.
I suspect there's a reason the top brands – RRS and Gitzo – use twist locks.
I prefer no center column (or optional) and availability of a leveling base for using a gimbal or shooting panos.
I totally agree. I took Neuro's advice on the leveling head and it makes all the difference- amazing.