novice questions about glider instruments

1.Why do many gliders have two variometers?

2.Assuming for a moment that you are not flying in the flatlands, how often and under what scenarios do you use your compass? What are some good exercises for developing airborne compass skills?

3.If you needed panel space for a PowerFlarm display, which existing instrument would you delete (if any)? (Assume a PDA is present.)

I've my own answers already of course, but I'd like to have the benefit of your experience/insights.