The insulation thickness appears to be the same for both up through 34.5 kV. However, the overall diameter of the XLP cable is slightly larger. This may be due to a slightly thicker conductor shield (semi-con) layer for some reason.
I'm still getting up to speed on these, but we are getting some XLPE and some EPR cable for 11kV. The compact EPR is smaller than the equivalent XLPE, but part of that (and the reduced cost) is coming from the elimination of water blocking tapes we specified on the XLPE. We still can't really get a cable to match (or exceed) the rating of the older paper lead cables in city ductlines with small diameter ductlines, without going to higher temperatures, and we're still working on derating factors due to mutual heating.
