Are wider skis like the Bent Chetler 120 good for beginners?

Generally no. A 120mm-waist ski like the Atomic Bent Chetler is built for deep powder and soft snow, and it feels sluggish and demanding on groomed runs where most beginners spend their time. New skiers are usually better served by a narrower, softer all-mountain or front-side ski such as the Atomic Bent 85.