I first noticed the difference that having the right kit for the job can make when I moved from using an old pair of skate style trainers to proper flat mountain bike shoes in the form of the Shimano AM41s.
Do you have experience of both clipless pedals and flats?
As you continue on riding, you will eventually be able to experience both pedals so you will be able to firmly decide on which to use or you might switch back and forth between the Mountain Bike Flat Pedals vs Clipless.
The clipless vs flats debate is just too rider subjective. I prefer clipless because i like that connected feeling to the bike, especially in the rough, i dont worry as much about my feet coming off the pedals.