I wish people would stop stating this as a fact. It is a matter of opinion. I for one find Mk 4s and MK3's quite uncomfortable.
It is also interesting to see that yet again, folk have disappeared down a rabbit hole on the back of a speculative articles.Some folk are talking as if LHCS was a done deal.
By comfort I think people mean that there's little underfloor vibration, which transfers to ride comfort, rather than the internal fitting of the vehicles. The part that there's less underfloor vibration vs vehicles fitted with engines underneath, is pretty much fact.
It's far from a done deal for sure. Presumably one of the prospective bidders is coming up with something loco hauled for this to be a story.
However it read from the XC franchise info like there won't be any firm requirement for new stock although obviously this is yet to be confirmed for sure.
Presumably the attractiveness of loco hauled is due to the speedy delivery time if using existing locos. The TPE mk5s are apparently ready for testing on the WCML imminently and that's a fast lead time in today's industry.