Hi, I don't know if anyone can actually help me, I've looked this up everywhere but can't find it.

I redid the initial vault twice with 2 characters (I like to restart the game once I know the game mechanics a bit).

The second time I did all combat in the Vault using VATS and I noticed that I barely got to the half-way mark of level one while I got 1 level (Got to level 2) by the time I finished the vault when I didn't use VATS on my first time through the vault. Did anyone notice if VATS generate less or no experience?

I think the rate you accumulate exp is conducive to your Intellegience in SPECIAL, not anything to do with VATS. Did you allocate fewer points in Intelligence the next time around?

As RibFeast said, Intelligence affects XP gain, so that's the most likely reason. I haven't seen any change in XP in or out of VATS.

I allocated the same intelligence in the second time...

From my understanding I did everything there was to do both times going through the vault.

I really can't see a difference apart for me using VATS> I may test it again with another area. Clear it with VATS and without.