Consider this scenario: I want to get the quadcopter up some meter..quite far, not very high but beyond the height where it becomes hard to see its rotation and whether it goes up or down.
1. Put it in Loiter mode and use the throttle to rise, but what do you do when you want it to go down again? If you cant see how fast its going down, how can you get it safely down? In loiter mode, will it fall to the ground if you set throttle to 0 or will it glide down as fast as possible without falling?
2. Or should I use the Position mode to manually use the throttle? But this sounds much more dangerous..
when I do a fast decent I pitch the quad full forward and reduce power till it starts to buffet around.. then increase throttle slightly till flight gets stable... then I fly a downward spiral till I get to the altitude I wish.
the other option is get telemetry and learn to fly on instruments.
You can use alt hold. Tune and try it where you can see it, and make a note how much throttle you need to descent at the wanted rate. The same goes for Loiter mode. You can set your transmitter to trigger the predefined throttle at a press of a button if you want. But for the sake of god do _not_ try to land while in alt hold :-) I learned the very hard and bloody way.
Btw, I also test stability of my setup by killing the throttle completely and then recovering after a while of it falling - good stress testing (both the copter and the pilot ;)). So far, it always recovered but you should NOT do that regularly.