Flew most of the OW carriers in F. I am 6 ft, so length is not a problem, but width.

Here my comments:
Seats on BA and QF are almost identical. The lauyout in the 747 is different: BA has 5 on each side and two pairs of 2 in the middle. QF 4 on the sides, 3 pairs in the middle. 14 seats total, seats fairly narrow, some seats are extremly narrow close to the walkway (especially where your feets are). Better privacy on single seats on BA because of the layout.

IB and LA have 2-1-2, feets are not boxed in. More space, but less privacy. Likely better for tall people. 767 and 340 seats on LA seem to be identical in width, on the 340 (wider plane than the 767) there is an extra storage container next to the middle seat.

CX has 12 seats on the 747, actually my prefered seat for sleeping. Wider and more space around than BA/QF. 4 across on the A3x0. Only negative: very small armrest between you and the aisle, so people walking by are more notiacle.

AA: depends which config you get. Suites are nice, old seats are fairly narrow. I try to avoid them, because you are never sure which seat you get and also because of food/service/attitude etc.

Generall the seats which just move back (IB,LA,LH) give more shoulder/arm space than the seats which move forward (CX,BA,QF,SQ) because the armrests dont interfere