That’s where Bayesian reasoning comes into play, where there are prior assumptions (e.g., that engineered reality is strongly biased towards simple patterns) which make one of these hypotheses much more likely than the other.
Deciding that they are both equally likely is also a deciding a prior.
Yes, "equally likely" is the minimal information prior which makes it best suited when you have no additional information. But it's not unlikely that have some sort of context you can use to decide on a better prior.
