Ancient Mark 3s with not brilliant ride quality hardly offers a better environment.
People who've used 170s regularly and now use the refurbished HSTs disagree. Their only complaint is that there aren't more.
Transport Scotland wants the Inter7City services to have high quality rolling stock providing an inter-city standard environment. It's actually very similar to TPE in a lot of respects. So the options TPE have gone for will repay a look. Class 802s are probably overspecified (125mph bimodes) and might have been problematic on the Highland Main Line, but were apparently proposed by one bidder. Another apparently chose Class 68s with LHCS, a definite possibility though we know now that Mark 5 coaches can be problematic. And finally Class 397s, obviously electric-only but a modern intercity multiple unit from a family that has DMU members. Presumably, CAF could have done something using Class 397 bodyshells and the Class 195 traction package; with Scotrail having a year's head start on TPE and Northern, they'd presumably have had a decent fleet in service for December 2018.
Of course, if they'd been delivered on the timescale of the 397s and 195s, the stock shortage would have been
even worse than that now being seen by Scotrail, with no possibility of getting in unrefurbished HSTs to cover for it. And we'd probably be screaming about how silly they were for not getting proven HSTs that only needed refurbishment.