Your chances of being on a non updated interior are very slim, only three ETOPS -800's are still in the old configuration.

On the updated (Recaro) interiors, all the exit row seat bottoms are .7" lower. This is accomplished by using a seat pan, cushion and cover. The rest of the seats including row 6, use fabric stretched over a aluminum frame with a padded cover over that. So, due to the differing designs you can't assume one is more comfortable than the other. This is not the case with the older seats. They have lower seat bottoms at A/F exit row seats. This is attained by having a thinner cushion, so it can be reasonably assumed they are less comfortable than the rest of the seats.

Another difference is the airbag seat belts at row 6, some people don't like the extra bulk.