Couple of things I have noticed...
The Anvil-30 doesn't seem to get as dirty as the other heads from RRS. I have shot off a number of RRS head that were sent as loaners for use on stages at events, and had a friends get very dirty. When both the leveling base and BH-55 get dirty they really suck to shoot with. They get very stuttery when moving (not smooth). The fix is to clean them. I have shot my Anvil-30 now at 4-5 matches in very dirty conditions (Quiet Riot, Dog Valley, Heatstroke etc), and zero issues with the head getting dirty. This is a great benefit I think over the other options, HOWEVER I would prefer to use it longer to see if I can get it dirty enough to start manifesting the problem.
The choice of legs on the tripod for me was a no-brainer. 3 series legs, in 3 sections. For me, the entire question was one of stability, stability and lastly stability. The 3 section 3 series is the most stable between the 2 series - 3 series and 3 section vs 4 section.
If you extend all the legs, the 3 section legs have larger diameter legs in contact with the ground, and that makes it more stable (less vibration etc).
There are benefits to running the 3 series, 4 section legs, for me basically that it compacts a bit more for packing. The 4 section legs weigh more, so you should balance that into the equation. When I measured them side by side, it as about a 1lb difference with the 4 section leg tripod setup being 1 lb heavier.
These sealed the deal for me, and I did 3 series 3 section legs with Anvil-30 conversion kit and head.