I find the OTO test kit included in the TF100 kit to be handy for quick ball park chlorine level checks, but it is a BIG ballpark and it is also handy as a double check against the FAS-DPD, I have used tests that were DPD in the past, they are somewhere in the middle, a little easier than doing the FAS-DPD, but have the color matching problems of OTO.
So
OTO - quick easy 1 step ballpark total chlorine number
DPD - mid level test but tells you both FC and CC (at least in a ballpark)
FAS-DPD little more work than DPD, but tells you to the .5 PPM level for both FC and CC and best of all NO COLOR MATCHING just pink or clear