If you look at the aircraft type and the number of seats you will get a good idea of comfort.
On a given type unless there is a class mix difference or a clear SIX seat difference in seat count (i.e. a row) then the seat pitch is going to be very similar.
A modern seat will have a slimmer seat back and better cushion forms. So with the same pitch you can have more comfort.
Seat width varies between types (A320 wider than 757/737 etc) but seat width also varies for different carriers with the same type because the seat manufacturers are not the same. (Remember the aircraft OEMs do not make the seats despite the general public's view.)
Unless you have a detailed seating layout you will have a hard job identifying the extra pitch.
The exception is on airline like BA that have variable geometry seats that concertina from 5-abreast in Business to 6-abreast in Economy. In this case the pitch is
probably better (or at least equal) in the front of the cabin.
http://www.pprune.org/forums/showthread.php?t=40675 In this case you should aim to sit in the double seat just behind the curtain on the PORT side. This is because this seat is in Business class configuration to reduce the kink in the aisle.
A good seat is a personal preference: Window, aisle, bulkhead or e-exit and depend if you are travelling alone or as a couple/family.
How much do you want to pay for more pitch? In this day-and-age of Internet sales
the best price, at the right time of day is often the best seat.