You can be assured I did measure it with a digital tape measure! Using published pitch figures isn't going to help much given there are 3 different seat widths on BA and 2 on U2. One other factor, incidentally, is that the BA seat curves inwards more sharply at the narrowest point, whereas U2 have that string vest thing on their seats (and their magazine is very thick!). However I measured with U2 seat pocket empty.

I do agree this is a personal interpretation in one sense - some seats work better for different people. But the knee room at every point on BA is greater than U2, and significantly so on bulkheads and exit rows. I have measured it on over 20 aircraft. Leg room is about the same.