Can med schools judge based on 4th A-Level grade?

Like would they be more likely to accept you if you got AAAA than if you got AAAC or are they only interested in the first three??

They only want grades that match their requirement. Let me give you an example. If you wanted to study medicine and the requirement was AAA and u got A*AB they should let u in as those grades are equivalent to their requirements.

I hope this helps!

Medicine degrees do not usually apply equivalence, nor use UCAS points
If they ask for AAA, they want AAA and whilst they may accept A*AB, there are many rejected with these grades every year.
To answer OP's question, they will only look at your 3 relevant A levels, but some med schools use the whole UCAS application in the event of a tiebreak

When I look at most uni websites, they allow equivalance

2 or 3 do. Can you say which are “most”?