Making that decision can depend on how you breathe... For instance, do you breathe through your mouth rather than your nose, or do you tend to get a blocked nose?
If you know you have no problem breathing through your nose when wearing a mask, you should be able to use a nasal pillows mask or nasal mask. If you breathe through your mouth (sometimes referred to as 'mouth breathing'), you can try a full face mask or a nasal mask with a chin strap to stop your mouth from opening during sleep.