- English has complex morphology and less rigid phonology.
- English has less complex phonology but more rigid morphology.
- English has both rigid and complex morphology and phonology.
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I have to say this is a very strange question. You are comparing apples and oranges, and to what end? Rigidity and complexity are two different and unrelated characteristics. Therefore, in order to make the comparisons you seem to be trying to construct, you must eliminate one or the other from each statement, OR you must include both.
Here are some examples of valid constructs using some of your elements:
English morphology is complex, but not rigid. English phonology is less rigid than its morphology. English phonology and morphology are complex and not very rigid.
Notice how you can use both adjectives only if you have them refer to one noun (or both nouns considered together), and you can use both nouns separately only if you describe them with only one adjective. Or you can make multiple statements and link them into complex sentences, but the basic constructions must remain as I stated them.