Doing cardio exercises daily effective or not?

I m 16 yrs old, height 5' 9" and weight around 78 kgs... I m thinking of slimming down and for this purpose i m walking/jogging 4-5 kms daily... Cud sum1 tell me what is more effective?? Doing cardio exercises daily?? Or doing them 3-4 times a week?? Which is more effective and why??