Two-button style suits are better than single-button type.
Why do you think they are better?
Two-button suit is classic for all, its frame-length properties fits almost all types. If you have short torso, two-button suit is the go to option.
I do have a short torso and think the two-button suit looks better on me.
Mostly, top button should only be fastened when wearing it, if you like closed jacket.
Why is the bottom button not fastened?
In two-button suits the last button should never be done because the top button is done already and your jacket fits perfectly. If second button is done too, it worsens overall look.
I get it.  It might pull around my middle and make me look fatter.
Yes, It creates a baggy area and your suit might appear like a winter jacket.
That would be unattractive and really take away from the look I am going for.
You should also undo all the buttons when sitting, because if you sit while buttons are done, you might risk ripping your jacket.