to my knowledge
oneway: fast but a little tricky to drive. thats wot i race with
ball: user friendly but slower than a oneway.
spool: like a ball but better for braking and aggrresive driving style but s;low like a ball.
a ball diff will be easyer on frontend impacts so if you are a rookie i would start with a ball in the front.
chassis flex, is it carbon fibre or plastic?