Thanks Toby for great write up.
I use the gear diff on TB03 is was because much less maintenance than ball diff, it is not for performance gain at that time. we run few times in TQ but not much more. During practice for TCS national, we found the car is not much faster than ball diff in Tamiya track, and ball diff is easier to drive. But the gear diff can have same performance during three days race but ball diff not last.