the speed of which your cf bar goes up differently for each character.
The fastest would be for gohan. Krillin takes the longest I think. It also depends on the average pl of the server and if plcatchup is enabled.
If everyones powerlevel is high and yours is pretty low it will go up faster when you die. And that only works if plcatchup is on.
You will also get your pl to increase faster if you attack someone stronger then you.