I owned the Pass XP-15 for many years and have been enjoying the XP-27 for several. I dont find the difference between 15 and the 27 to manifest through different loading. The 27 sounds different (and a little better) at all settings. Like Lewn, I have never heard a big difference between 100 ohm and 47 kohm loads on LOMC carts. Like ssg308 reports, big differences in character can be discerned with different gain settings. My conclusions are that the Pass phono preamps can handle RFI generated by LOMC quite nicely.
Hoping that ssg308 enjoys the Unami Red.