I've just started playing through FFX HD Remaster on my Vita, and I've been beaten by the Luca Goers, aside from my wounded pride is there any reason I shouldn't just carry on? I know I can beat them if I try a few times, but I don't want to if there isn't a good reason.
The only gameplay difference is that winning awards a strength sphere. Strength spheres can be added to the sphere grid (in place of an empty location), which characters can then activate for +4 strength.
While strength spheres are rare, they are by no means unique, as they can eventually be acquired by killing Juggernaut in the Monster Arena, allowing you to obtain arbitrarily large numbers with enough time investment.
So long as that sequence of events hasn't been changed since the original release, the only thing that changes if you win is the cutscene that follows when Wakka bids his team farewell. If you win the match against the Goers, he hands his teammates the Crystal Cup, the champions' prize, instead of passing off a regulation blitzball.
Don't feel bad if you find it an insurmountable challenge, though. The Goers all have incredible stats for that point in the game; the prime example is Graav, who has about three times the stats of any of the Aurochs. Don't be surprised if the AI constantly passes him the ball, because he can basically trample your entire team if he feels like it, and the game will use that against you.