A married man is going to be more accepting of who you are because he's not looking for perfection, he's looking for companionship (not always just sex).
A married guy will also, mist likely not lie to you, as he's already had enough of that in his life.
He will hold no judgement against you, won't stalk you, and won't hog the covers at night.
He will support your endeavors, and respect your life as whole.
He has stories, skills and has less chance of giving you an STD, because he doesn't have the laundry list of partners a single person does.
Morality aside- we all have imperfect lives, it comes down to what you are looking for.
Easy choices-
for someone to marry - stay away from a married guy,
if you are looking because you are married too- married guy
Rebound guy? Married
Fun and need discretion- married guy
Don't want all kinds of heavy clingy stuff.... Married guy
I'll probably get flamed- it's ok- I have a flame retardant suit on.