Theory: Which is better?

Is there a difference in the following events:

For Each BulletObject: ----------- Subtract dt from BulletObject.Life

...compared to...

Every Tick ---------------------------- Subtract dt from BulletObject.Life

They seem to do exactly the same, and in used in such a basic manner there seems to be no difference. Does one use more overhead? I always heard that "for each object" could take time to loop through, but isn't that the same as looping through the list of picked objects?

For each is for uses where the events are not looping through all the instances (I cannot think of an exemple right now other than the on timer condition), use the everytick in that case, since they are all picked and executed together