I am currently working on a DP2 finder (F2S). It is sensitive down to 8 seconds, or was originally. Now 45 years later I believe I'd stay away from it and stick with the DP1 or go on to DP3 or DP12 But then I'd still stick with DP1. The LED finders are hard to see in sunlight. Besides, what good is sensitivity down in extreme low light? Because down there, film reciprocity problems have kicked in. So what good is it? LED requires more power, not less.
Edit: I don't know why DP1 only goes down so far and DP2 goes farther. They both have CdS cells, so why can DP2 go lower? I speculate that the metering circuit has some amplifying capability. But then...there's that reciprocity thing again. Nah... I'm done with DP2, 3 and 12. A meter movement is a simple circuit and very dependable. Although if somebody put an F2Sb in my hands, I'd take it. Rare and collectible.