Generally I'd perfer.

Competition: 3 balls, no extra balls.

Public coin-op: 5 balls, extra balls (with a limit of 1 extra ball or maybe 2).

Adjust playing times by the difficulty. On individual features if necessary. As well as tilt sensitivity and steepness.

Reason being, that a payed game is much more appealing, when you feel a certain progress through the game, with modes, mb etc. Hence a 5 baller is more fun than two 3 ball games. Especially for machines you don't know. The limit on extra balls is a fair trade if necessary.