There are an infinite number of models that can predict 10 variables, or 20 for that matter. The only probable way for scientist A to predict a model out of the infinite possible ones is to bring prior knowledge to the table about the nature of that model and the data. This is also true for the second scientist, but only slightly less so.

Therefore, scientist A has demonstrated a higher probability of having valuable prior knowledge.

I don't *think* there is much more to this than that. If the two scientists have equal knowledge there is no reason the second model need be more complicated than the first since the first fully described the extra revealed data in the second.

If it was the same scientist with both sets of data then you would pick the second model.