The coordinator goal is obviously more difficult for the reasons stated above.
Pokemon Contests are only held once a year in each of the marked locations. There can only be one winner in each Pokemon Contest. Coordinators like Dawn, Zoey, Jessalina, and Kenny have lost at least one contest in the Sinnoh Region. The Pokemon Contests have an appeal round that will eliminate the bulk of the competition before the battling rounds can truly begin. At the very most, only eight registered contestants will advance to the battling rounds in typical contests. 30 or more coordinators will attempt to register for each contest. Well over 200 coordinators in each region may be eligible to compete in regional Grand Festivals. In the Sinnoh region, some contest halls might host double performance appeal rounds, intensifying the competition by placing further emphasis on how each pokemon can shine.
As a result, there will be a greater priority for coordinators training alongside their pokemon and attempting to perfect combinations. There is a lot of uncertainty in the contest arena, as the coordinator will have no idea who he or she will be competing against in contest battles and/or appeals. This lack of information or knowledge beforehand may make or break the coordinator's success rate, as opposed to a pokemon trainer who may be acquainted with the gym leader prior to the start of their match.
When one competes for Gym Badges instead, there will be less pressure on the trainer's behalf. If a trainer loses against a Gym Leader, he or she can simply rechallenge that Gym Leader at a later time. Furthermore, there will be less hassle on the trainer's part because Gym Leaders have relatively flexible schedules in which they will be able to battle challengers. There will always be Gym Leaders who will abandon the maintenence of their gyms or deny requests from challengers for personal manners, but such cases are very rare. [In the Kanto region, the Pokemon League Association penalizes gym leaders, or during extreme measures, shuts down the operations of pokemon gyms entirely if gym leaders do not adhere to their guidelines.]
Most Gym Leaders tend to specialize in one type of pokemon attacks, giving the challenger some flexibility in selecting which of their pokemon can be used in battle. These matches are typical 3-on-3 eliminations with no time limit, but may even be as large as 5-on-5 and 6-on-6 full battles. Contest battles tend to be 1-on-1 eliminations with a 5 minute time limit, adding more pressure on a coordinator to advance to the next round. In addition, gym challengers may be given the luxury to switch out their pokemon. This luxury is something that the gym leader may be denied. Of course, certain gym leaders like Lenora were able to switch out their pokemon against their challengers. This luxury is typically provided to the challenger regardless, but it may or may not be an advantage depending on the circumstances of each individual gym's rules.
The only disadvantage that a trainer has against a coordinator is the number of tokens that are required to enter the regional competition. Pokemon trainers need at least eight badges to compete in their regional league competition, whereas pokemon coordinators will only need five contest ribbons to compete in each regional Grand Festival. Of course, given the restricted nature of pokemon contests in general (as well as the number of contests that are held in a region each year), this "advantage" should also be discarded.
Pokemon trainers have a greater opportunity to reach their goal. That's not to say that coordinators aren't capable of reaching the Grand Festival or become the top of their class. This goal will require much more time and focus since pokemon contests not only judge the succession and efficiency of a pokemon's attacks, but will also judge the way a pokemon dodges or counters an opponent's attacks. Pokemon coordinators will be penalized if their pokemon's attacks do not land a hit against their opponent's. Pokemon trainers can simply disregard this and continue their battling.