I ordered Elka Stage 1s for my P520. The main reason was I wanted a better ride. Between the short sidewalls of 24" tires and the hard shocks, our first few rides in the Colorado Mountains near Leadville were pretty bad. So, after swapping tires to radials and a much larger size for more absorption. I knew the only way to improve things further was to swap the shocks.
I chose stages 1s because I didn't feel I would ever change the settings other than preload. To be honest, I have a hard time spending $2k on a set of shocks for a machine that has a sticker price of $10k. And, as others have pointed out, we only have 5.9" of travel to work with. If I had a machine that cost $20k and had 12-14" of suspension travel, I might be more inclined to look at other stages.
I'm looking for an improvement in my ride, not the ultimate in adjustability. These machines are fairly simple so I thought the Stage 1 was appropriate.
Rob