Between the maxillary first molar and maxillary first premolar, which tooth is generally considered more anatomically complex/challenging for endodontic treatment?

The maxillary first molar is generally considered more anatomically complex for endodontic treatment than the maxillary first premolar, given its typical 3-4 canal system (mesiobuccal, distobuccal, palatal, and a frequently present additional MB2 canal), curved roots, and narrower canal anatomy — compared with the first premolar's typically more straightforward 1-2 canal system.