It's funny you ask this question. I did a bit of gliding when I was about 15 purely 'cause of the great price. The training for glider pilots, I think, is far more comprehensive in ways. For instance, you have to be able to recover from spin, land after practise cable break(although you'd never turn back with a powered craft below 1000ft!) Circuits are no problem to you 'cause you have to think about them so much more when gliding and consider your proximity to the airfield. Your knowledge of weather is more atuned 'cause of risk of looping on the ground run due to crosswind if a wing drops, turbulance going trough tree height, thermals, down drafts and just being able to feel almost every gust up there.
I only got about 20 glider flights in while I was doing it (10hrs approx.). I never went solo but what I learned helped me enormously when it came to doing my PPL. I got solo in my 7th hour PPL which is good going.
Highly recommended for all!