Hard to tell - if you are already a microlight pilot, and current, it might help. If you aren't a current pilot, it'll probably increase the hours as PC based sims used unsupervised will probably introduce bad habits that need unlearning.
At your age, and not flying yet, I suspect neutral - you'll have a lot of bad habits from the sim flying, but are likely to learn very fast if you apply yourself now. Good youngsters usually learn not far off minimum hours.
G