Mt personal experience with regard to dynamic range is:
XP1 is equal to the D700 (but different), these are approximately 1 stop better than the X100.
The X100 beats the D300.
Everything, including the D200, decimates the first generation m4/3 sensors.
The D700 looses highlights well before the XP1 while the D700 shadows hold up better. I use a more exposure with the XP1. My speculation is the XP1 and D700 have almost identical dynamic range, but the useful range is spread over different EV values scales.
The overall noise performance of the XP1 with the 35/1.4 is very close to the D700 with the Nikkor 50/1.8 G when both lenses are wide open. The D700's increased surface area is offset by the larger aperture of the Fujinon. The total number of photons recorded with optimum exposure is similar... as is the noise. The newer sensor design probably compensates for the 1/3 stop difference between the lenses.