Crocheting: 'knife' grip vs 'pen' grip
Practicing with both common grips is a good strategy.

While you will naturally develop a preferred grip for most projects, having a variety of approaches you are functional with will make a much broader range of thread weights and project weights possible for you to accomplish with some ease.

Also being able to alternate approaches will go a long way toward reliving tiredness and joint strain on big projects.

Short answer:  BOTH in combination are better than either alone. 

It sometimes helps to wind a small scrap yarn ball around your hook that will fit comfortably into the V formed by your thumb and index finger metacarpal bones. There are commercially available hook designs that accomplish similar aids.