Oh good grief, if you think that's a genuine photo you really shouldn't be perusing a professional aviation website.
Now then, may I try to answer a few of these questions? I'm not saying one is right or wrong, what I'm saying is that soem of the differences in weight come from the design philosophy.
The A320 has a larger engine fan diameter than the 737 (any denomination) even though, nominally, they have the same CFM56 engines (the core of the -5 on the A320 is the same as the core on the -7 of the 737NG. The cores are the same, the fans aren't). Why is the fan diameter greater? Well, the -5 engine on the A320 has a higher bypass ratio than the -7 on the 737. That has 2 benefits - 1) the A320 engine has a lower specific fuel consumption and 2) the A320 engine runs cooler and so stays on the wing longer (greater EGT margin) which gives lower engine maintenance costs. So the A320 engines burn less fuel than the 737 engines and should cost less to maintain. The penalty is that the A320 needs a taller landing gear for ground clearance of the engines, so the gear is heavier than a 737 (weight penalty). The A320 has a greater fuselage diameter than the 737, so it will necessarily have more metal in it. It also has main landing gear doors to try to improve the aerodynamics (but they weigh something, of course) whereas the 737 wheels and wheel hubs sit partially in the airflow, so you get parisitic drag.
What you need to realise is that weight is not the be all and end all. The A320 is heavier than the 737. But the A320 engines burn less fuel and the aerodynamics are slightly better (yes the 737NG had a new wing, but Boeing were limited by the interface with the fuselage, as it didn't change, so they were forced to compromise by the constraints imposed on the spar positioning).
Swings and roundabouts that, at the end of the day, mean that they are both very close in fuel burn - and that's what counts these days.
I hope that's quite clear. And the company I work for has the A320 (and A319).
p-k-b