It depends really...
THE PHOTOS ARE NOT MINE I TAKE NO CREDIT:
Mallard Seats: Brilliant for long distances in Standard. My favourite one.
https://www.flickr.com/photos/matthewbaxterrailways/24383276786/
IC125 Seats: Quite comfortable I suppose. Armrests bad. Not good for tall people.
https://www.flickr.com/photos/ardcoasters/6973908799
Grammer HST/158: Popular but I couldn’t sit on those for too long.
https://www.flickr.com/photos/nuuttihyttinen/6515542987
Grammar 350/380/444: Good for journeys up to about two hours (three hours on 444s)
https://www.flickr.com/photos/rail_scenes/9988583835
Chapman seating as in 143, 150/2, 317, etc. They’re quite comfortable but I wouldn’t put up with them for more than an hour.
https://www.flickr.com/photos/42767052@N08/27165153354
Richmond seating as on board GWR 153s and some FGW Dynamic Lines refurbished 158s - better than the above. I’d willingly do Plymouth - Penzance on a 153, I prefer those over 150s anyday. I love the 143s the best in Devon though!
https://commons.m.wikimedia.org/wiki/File:BRC153Inside.JPG
Original 158 seating is even better than that, it is plump and cushiony, really comfortable. Only problem is trains with those seats never have much legroom. However I find GWR 158s have better standard seating than the HSTs!
https://www.flickr.com/photos/rorymacveii/8728489066
Desiro 3x2 Seats are very uncomfortable- I use SWT/SWR to travel to Waterloo from Woking/Aldershot/Farnham/ Farnborough or Guildford upto four times per week - always aimed for the 159, then the 444, with the 450 last. Don’t like 360 seats either but if travelling to Colchester I’d choose a 360 over a nasty “Dusty Bin”. I’d take a 90+Mk3 though.
https://commons.m.wikimedia.org/wiki/File:Class_450_interior.JPG
The seats featured on 321s, 319s, etc are really bad. Seat cushions come off, they have 3x2 seating, etc.
http://www.train-photos.com/picture/number13254.asp
Networker seats are also horrid.
https://commons.m.wikimedia.org/wiki/File:465907_Standard_Class_Interior.JPG
Fainsa seats I actually quite like! They
are harder on 700s than 387s though.
https://commons.m.wikimedia.org/wiki/File:British_Rail_Class_387_Interior.jpg
I also like the typical Electrostar seat such as that featured on the 375 and 377/1-5. The one that LM and SWR 450s use in first class.
https://www.flickr.com/photos/rorymacveii/8714304546
I don’t know what type of seat the 379s use but it’s very nice indeed!
https://www.flickr.com/photos/34261415@N03/22912778190
Pendolino and Voyager Seats I actually like, the sort of curved head thing at the top is full of soft padding and I always feel comfortable in those seats.
Btw all you haters out there who say you hate the plastic, I’m fairly sure the seat back is metal. Painted cream.
https://www.flickr.com/photos/emdjt42/15610900973
Hate turbo Standard class seats but love the permanently declassified first class.
Original Standard:
https://www.flickr.com/photos/londonbuses72/14370236826
Permanently declassified First:
https://www.flickr.com/photos/71625163@N02/28968256116/in/pool-gwr/
First class at the other end (not declassified) is the same but with cream leather seats - talking about the refurbishment here.
https://www.flickr.com/photos/71625163@N02/28383479183/in/pool-gwr
Class 168/170/171 seating is just wonderful. Although on the exTPEX 168s (the ex ex SWT 170s) they have some nasty hard design which is different to the usual and I don’t like it at all.
The nice original 168/170/171 seating:
https://www.flickr.com/photos/34261415@N03/18771454326
Some 168s also feature the same type of seat as a 442. These I don’t like as much but they do have more support if you are tall I suppose.
https://www.flickr.com/photos/76437498@N03/9721623102
And then the unpleasant 168/3 ex TPEX (ex ex SWT 170) Seats i was talking about are featured on this video:
Adelante and Coradia Seats are pleasant enough, overrated really but if in Standard class I’d take a GWR 180 over a GWR HST probably. In first class it would be the other way round most definitely.
http://www.flickriver.com/photos/mk_tom/23471514906/
Nearly there now (sorry for the length)
345 Seats. Fine for the journeys they will be doing.
https://commons.m.wikimedia.org/wiki/File:Class_345_interior_7th_July_2017_15.jpg
332 I go First with HEx so I don’t know about their standard really but it looks like it could do with some tables, though it does look quite good. (Better on the internet than in reall life those)
https://commons.m.wikimedia.org/wiki/File:332002_DMSO_Interior.jpg
Juniper seats (334, 458) Really like these! The squashy headrest is very good! Remove the grab rails and add tables and armrests as per 460s and I’d take on happily on a Weymouth service over a 444. Yes I know they don’t run on that route!! Best 3x2 - joint with the ones below.
https://commons.m.wikimedia.org/wiki/File:458015_A_Standard_Class_Interior.JPG
318 seats:
These are featured on some 317s too. (Some have these seats some have Chapman seats in 2x2) I like the squashy feel to these, best 3x2 out there - joint with above.
https://www.flickr.com/photos/24772733@N05/33613982611
And to conclude, in my opinion the worst seats in Britain. That of 315s, 314s and some 313s.
https://www.flickr.com/photos/91974242@N04/25959947854