Seems like preference to me...I like 2 gear diffs, but that may be the way I drive. I have had a fast guy tell me he's always faster with a spool and ball diff, but he said he's driving hard enough to pick tires up and the gear diffs unload on him. At the same time, one of the local fast guy's car looks like a 1/12 on rubber tires on asphalt and he has 2 gear diffs. ???

???
You might just have to try it and see if you like it.