The PAL Action mode is different in that it is independent of the save file. You start with minimum max HP and there are powerups which raise it. Also spells can be found as powerups as well (from what I read, the Pro Mode in JP/US is no magic)
I think you also get 1-Ups for certain points (20,000?) but no continues (whereas arcade would let you continue, since of course it wants you to put more coins in the machine).
From what I understand, NSS could be set to "skill" mode (where you need to insert coins at game over) or "time" mode (where coins are only good for a certain time).
The one actual NSS machine I ever played was set to time mode, and only to give one minute per credit.