BDR-XD07* external drives

Does someone know what the real differences between the BDR-XD07J-UHD, BDR-XD07BK, BDR-XD07R and BDR-XD07W drives are??
They seem to be 2 different XD07 types, one standard (in black, white and silver) and the BDR-XD07J-UHD, especially announced for UHD playback.

“Pioneer BD/DVD/CD Writer BDR-XD07J-UHD (BLACK) [Japan Domestic genuine products]” explains a bit.