No downside. Start your best players (or alternatively, start the players with the most growth, if you choose to play for the future and have the players to reasonably make that play). Or mix it up. Sometimes upperclassmen will complain and lose work ethic if they go the other way, if their PT drops. But that doesn’t really hurt in most cases, since upperclassmen are usually developed in important areas anyway, if you’ve managed their growth well for the first couple seasons. So basically don’t worry about moving guys in and out of the lineup throughout their careers.