It's really special, they did a killer job.
100% get the Stereo, the Mono actually strips out a lot of the effects, it's a different cut with a different length and just misses that this record was specifically designed for stereo, Jimi heavily experimented with Stereo effects in a lot of the tracks.
You get a lot of people pitting it against the 2010 Marino cut saying that the UHQR at $125 is too expensive, but they categorically also state the Marino is about 90% of the SQ. I looked it up and to find a sealed copy of the Marino from a reputable Discogs seller is going to cost over $100 these days anyway, whereas you can now get sealed UHQR's for $110, IMHO, this easily wins out.
Plus it's the old dowell boxes which I wish they'd go back to, not a fan of the Mofi copied new AP boxes.