Indeed. There have been many posts on this "what's the best aircraft" topic, but please realise that what Boeing and Airbus provide as manufacturers is essentially an empty aluminium tube. It's up to the customer, the airline, how they fit it out, and the interior spec is still done individually for each airline, and there are a range of interior and seat manufacturers.

As time has gone on specs have got more spartan, which may go some way to explain why slightly older types like the 747 are often preferred over newer ones like the A340. Once airlines decide on a spec they normally stick to it for a long time even if they have changed things elsewhere on newer types, as there is an advantage in having a whole fleet to one spec so they don't get interchangeability problems. It's quite expensive to refit internally which gives problems if an airline starts picking up secondhand units.

It always surprises me for example going from the UK to Australia on Cathay Pacific how the B744 has been fitted in Y with seats that feel much better than the same airline's A340s, which are employed on comparable length routes. One trip I had a good explore round both (it's a long flight, nothing lse to do !) and found the Boeing's seats (manufacturer unknown) just seemed better done than the Sigma (a Spanish leading seat manufacturer) product in the A340, although the latter looked lighter and certainly cheaper.

Because I like a window seat the 767 (2 seats in 7) is better than the 777 (2 seats in 9) and both better than the 747 (2 seats in 10).

For narrow-body aircraft Airbus have a definite advantage over Boeing as their cabin interior is 6 inches wider, giving an extra inch per seat, which is quite noticeable. Boeing has stuck with the same size since the 707 in the 1950s; in that time the average size of people in the Western World has increased quite a bit !

For fun, try the old Soviet Ilyushins and Tupolevs. Plenty of legroom there !