by kullery » Sun Feb 28, 2021 5:34 am
AIM 5−1−8 a3 note 4.
“It is recommended that pilots file the maximum transponder or navigation capability of their aircraft in the equipment suffix. This will provide ATC with the necessary information to utilize all facets of navigational equipment and transponder capabilities available.”
While you may plan to fly a certain altitude, filing with your maximum capability increases options for any potential diversions.