Dynamic Range (R128) is a statistically weighted measurement of dynamic range, which describes the difference in volume between the loudest and quietest parts of a track.
This is measured in Loudness Units (LU) which are equal to decibels.
Dynamic Range (DR) is actually not a measurement of dynamic range at all - it is a measurement of the
peak-to-loudness ratio, as popularized by the "
TT-DR" tool.
Dynamic Range DR's measurement compares the difference between the peaks and the average loudness of a track, which is usually a better indicator of how "dynamic" sounding or "compressed" a track is.
Generally higher values here indicate a track with better mastering if you are comparing two versions of the same album for example.
However, there are some limitations of the tool. These measurements are not valid when measuring vinyl recordings (DR values are always reported higher than the CD) and while higher is
generally better, it doesn't always correlate to mastering quality.
As long as both values are high (above 10) it's possible that a track with a slightly lower (1-2) DR value will sound better to you.