The key word in this topic might be "and", not or. It's called scanning, and is being learned in IFR school lesson 1.
You have to have several parameters under control, of which the most important are:
- visual cues
- wings level
- rotation speed (3°/sec)
- correct attitude
- speed
- yaw
- thrust
All these parameters cannot be monitors solely in- or outside. That's why, you have to glimps in and out.
Dani