Firstly since there seem to be multiple meanings of "substrate" and "superstrate" let me start by defining the terms for this question:
A substrate language is one that was in a place before a new language arrived and took over. An example is Dacian words in Romanian.
A superstrate language is one that makes inroads into a place where a language is already fully established. An example is English words in Romanian.
(Please alert me if I have started with a misunderstanding!)
My question is: do languages tend to absorb the same kinds of features from both substrate and superstrate languages or do they generally take certain kinds of features from substrate and certain other kinds of features from superstrate?
For instance, perhaps languages tend to absorb lexicon from the language that was there before them (substrate) but phonology from the new language on the scene (superstrate), etc.