There are a couple of different possible door configurations for the 752 and 763, and I'd like to know what the pros and cons of the different types are, and what would lead carriers to prefer one or the other. If I'm not mistaken, these are the different configurations:
752a: big door ahead of wings, two overwing emergency exits
752b: big door ahead of wings, big door aft of wings (A321 style)
763a: big door ahead of wings, two overwing exits
763b: just two overwing exits
763c: big door forward and behind wing (A330 style)
With the 752, I'd imagine you lose a row in the 752b configuration, but you also have greater spacing for the overwings in 752a. Is this a wash seat count wise, or is there a weight/cost reason to go with one or the other?
On the 763, the twin overwing exits would appear to be the best weight-wise, would the only compelling reason to go with the big doors be if you're planning on putting in more seats (e.g. big Y section, 8 across)?
Lastly, why do the A321 and A330 only have the spaced door configurations? I know the A330 has the option of a 3/4 size door 3, but the positioning is always the same. Could the 321 get away with the 752a style doors (same 321 front door, 320 style overwing), or are the production differences not worth the hassle?