So I'm very late to the party (story of my life) and hope I can stick around for a while, commitments permitting.
Obsession was the first UFO album I bought after hearing Cherry and Only You Can... on Radio Luxembourg (I think) after its release. I loved this new (to me) hard rock sound with a wizard guitarist to rival Jimmy Page or Steve Howe as my heroes at the time. None of my friends knew about UFO until SITN came out, which elevated UFO in to my top 10 fave bands, with (still) definitive versions of songs from LO and earlier; I slowly discovered Phenomenon to LO over the next year or two.
As SITN was raved about with my friends, we were quite floored with reports that Schenker had left. I doubted they would be able to get anyone as identifiable. Also, could their trajectory be sustained; Obsession was top 30 in UK, SITN was top 10.
NPTR was eagerly awaited, so when one of my friends bought it we sat round hoping for the best. Unfortunately the hard edge was gone and on initial hearing, so was the quality of the songwriting. We all slammed Chapman for not being Schenker, and George Martin for being too tame. Please bear in mind we were 17/18 year olds at the time. I didn't listen to NPTR again until...
Reading Festival, UFO headlined Saturday night (I think) and they were awesome. Opening with Letting Go and playing several tunes from this album, the NPTR songs were given their balls back and UFO proved that live, they could still show NWOBHM bands how to rock. Raymond had just left but Carter was a trooper and I revised my opinion about Chapman; the man could play. This album has aged well and there are some good songs on here. Letting Go, Mystery Train, This Fire..., No Place... it's just a shame about the lightweight production.
Around the same time as Reading that year, Michael Schenker Group was released to rave reviews. This was a bit of a surprise to me as a return to Scorpions hadn't worked and there had been rumours of supposed mental health issues etc. Not having heard anything from the LP, I bought it on the strength of Schenkers standing (IMO) and the reviews I read. So happy I did, as great new MS songs and guitar work almost had me feeling there were now almost "two UFOs". In fact I didn't see the album for a few weeks as my friends borrowed it in turn. The album has the harder edge missing from NPTR (I bet Roger Glover was far cheaper than Martin). Gary Bardens is not bad but no match for Mogg, so Into the Arena is one of my favourites here along with Lost Horizons, Victim of Illusion, in fact there isn't a bad song here.
So from the latter half of 1980, things were looking good for both bands in my opinion.