Piano competitions can be a real pain in the ass. Not just for the competitors, which is obvious, but for teachers as well.
Placing well often this means playing a piece somewhat conservatively at, say, 80% of a student's technical capacity. But improving can often mean practicing something at 90%, or even 110% capacity. (Within reason of course.)
Don't get me wrong I'm not against competitions. My more competitive students still enter them. But this "competition is everything" mindset some people have can wear thin; especially when it comes at the expense of real musical growth.
Developing musicians around the age of 13-18 need space to grow. They need to experiment, try out things, find their voice, and push up against pieces that might be a bit above their head both musically and technically. The fact is, this doesn't always lend itself well to polish and precision.
I'm not one of those people who is against competition per se, or anti-sports or anything else. But sports is sport and music is art. Art is a deeply personal thing, and the budding artist is finding himself through his practice. What are we teaching children when they work like hell on music they love, and then made to feel like failures because this or that judge was in a bad mood?
Long story short. Go and compete, but keep the big picture in mind. End of rant.