Clarify space vs. retrieval efficiency.

index.html

@@ -1149,7 +1149,7 @@ <h2>Multiple Status Entries in a Single List</h2>
 striking this feature during the Candidate Recommendation period since it would
 simplify the specification for implementations to not have to support sets of
 `statusPurpose` values in the status list credentials (again, a meager savings in
-complexity).
+space efficiency vs. retrieval efficiency).
         </p>
 
         <pre class="example nohighlight vc"