Distributor

I have decided to rework my dist..i picked a early 80,s dist and took out the upper half and took apart one from a 73 dist and look at the differance..slots are straight on the 8o,s dist and at about a 10 degree or so angle on the 73..iv made some plugs to plug and weld into the slots then ill remachine the new slots to shorten the advance curve .what diff is the the straight slot verses the angled slot.any advantage or disadvantage..anyone know why mopar did this..