I think you may be coming at this from a different angle to me, not that there is anything at all wrong in your approach. I'm looking at the whole product in terms of the majesty of the aircraft and its superb ride throough the skies, rather than saying "is this seat a bit better than that seat?". My perspective is that BA's WTP seat is now pretty much standard across the longhaul fleet, with only small differences between the A350 and A380 and any other version. It's essentially the same seat. They are all bulk produced, put on a chasis and slotted on to the aircrafts. The context of this aircraft is just very different. I know some people would feel - for example - the recline on the BA seat is better (or worse) on some aircraft - it's not - and / or on another airline - it may be so. But in reality very few people use these micro differences to lead to different purchasing decisions. The premium economy seats across airlines are all within a fairly narrow specification range. An A380 clearly brings in passengers, it's a popular choice of aircraft, but the fares are more influential than anything else.

I'd also be a bit wary of "newer is better"......