I was comparing the 377 with the 450
OK that wasn't obvious, but my post was also a statement about comparisons in general.
As far as the two that you are comparing, I find the 450s, (or in my experience the 350s including /1,/2 & /4 sub-classes) better riding than Electrostars, (377/7 on the same tracks). The 377/2s and 377/5s have mediochre performance on poor track being particularly susceptible to transverse shock. Although the seating in 377/5s and /7/s is firm and not to the liking of a few posters here, I think it is fine, even for journeys over 1 hour.
Other issues with Electrostar ambience are the squeak and rattle of their plastic trim panels and the virtually useless overhead stowage. Conversely, the noise from the older Desiros' air conditioning is excessive when at low speed or standstill.