The answer depends on your goals:

If you're planning to travel to mainland China or do business with mainland Chinese companies, learn simplified characters. This is what's used everywhere in mainland China.

If you're planning to travel to Taiwan, Hong Kong, or Macau, learn traditional characters. Those regions still use the traditional writing system.

If you're just learning for personal interest and don't have specific plans, simplified is generally easier for beginners because there are fewer strokes. Once you know one, it's not too hard to learn the other.