We usually use "that" or "those" when we repeat the noun(s) used before especially in comparative sentences.
But what about in this sentence?
The intellectually inferior mice achieved comparable performance levels to their superiors.
Or do I have to say this?
The intellectually inferior mice achieved comparable performance levels to those of their superiors.
Is the first version wrong or unclear?
achieved performance comparable to that of their superiors
achieved performance levels comparable to those of their superiors
performed (almost) as well as their superiors NOTE: depends on what you mean by "comparable" -- the same, or close?
Compare these actual attestations from Google Books showing the phrase headed by comparable coming after the first noun-phrase comparand:
... perform services comparable to those rendered by Company A
United States Internal Revenue Bulletin (2006) - Issues 27-35 - Page 290
... price ranges comparable to those being relocated
Wisconsin State Highway 23, Fond Du Lac to Plymouth, Fond Du Lac and Sheboygan Counties, Wisconsin: Final Environmental Impact Statement (2010)
... characteristics comparable to those of advanced successional stages
Plant Functional Diversity: Organism traits, community structure, and ecosystem properties, page 16. Eric Garnier, Marie-Laure Navas, Karl Grigulis (Oxford, 2016)
P.S. Here's an ngram showing the plural noun followed by the phrase headed by comparable side-by-side with comparable as premodifier of the plural noun followed by the prepositional phrase headed by to. For most of the 20th century the former has greatly outnumbered the latter form, though the latter form has begun to make some inroads recently: results comparable to those vs comparable results to those