Betamax, as released, was not better than VHS. It also had very low recording times of like 1 hour per tape.
Betamax was updated repeatedly, as was VHS. At no point was contemporaneous consumer Betamax able to match VHS for quality with the same recording times.
This is a persistent myth propagated primarily by people who have probably never seen Betamax in use.
Often people compare a professional version of betamax to consumer versions of VHS as well.
Betamax was better, too.