Virgin East Coast. end of discussion.
I've not tried post-refurb, but pre-refurb the single-piece cushions gave me serious back pain due to not supporting my back and under my thighs properly.
I'm going to vote for the GWR "tombstones" myself. As a taller passenger, it's nice to have a headrest on which I can rest my head. I also like these where used elsewhere, e.g. the ScotRail Inverness 158s (all of them in future). They just look good, too, projecting an image of high comfort compared with, say, the ironing board seats you get elsewhere. I like headrest "wings", but not when they are too low down and hit the backs of my shoulders, as the Mk2 ones and those used on most Turbostars do.
As for IC70s, there is only one thing to do with them - scrap. They might be comfortable for shorter, lighter built passengers (I don't mind the first class version), but for a heavily built and slightly podgy over-6-footer they are awful in every possible way. Though to be fair, where the IC70 cushion was used in the Mk2 shell without a centre armrest those were OKish.
Other honourable mention: the 2+2 Desiro seating, which also has small "wings" - ish. Hard but supportive and exactly the right shape for me.
Dishonourable mention: any 3+2. Disappointing that Abellio East Anglia are still talking about it in the new Aventras when every other TOC seems sensibly to have abandoned it, with LM having stated they regretted it on the 350/2s and said, and having stuck to it, that there would be no more.