I would consider checking vaccum on both cars with a gauge. (comparison) A small drop in available vaccum on the one with weaker brakes is all it would take. The vaccum booster would not give quite as much assist. Pretty easy check as well..These car are not new or at least mine are not. So I expect wear will be a little different from car to car automatically. Example: one car may have a vaccum pump in better condition or replaced/rebuilt at one point while the other cars pump may be starting to wear or in someway not providing as much vaccum because of leaks. Install a larger brake pedal? Sorry Hattersguy not stealing your thread guy just had a question. Great you missed getting entangled with everything but perhaps not your week to buy lotto tickets. Or on reflection maybe it is.