A personal journey through Karen's eyes

[Dom R]

Why does staying with one partner in spite of everything demonstrate "restraint"?

Err... if "restraint" == "self control", then I would say that would be a textbook example of "self control".
ie: "your body's hormones are telling you 'go screw everything in sight cause you havent gotten any in a year, but you choose to 'control yourself' and not do what your body is urging you to do."

As for your other question, of it being "better":

I'd say there are multiple reasons why it COULD be better, to be monogamous. but it's not automatically better.
To keep this post short and skip over the individual reasons... I'd say it's better at a 10,000ft view, when you are in a monogamous relationship where both people care about each other more than they do anyone else, and they also see to each others needs over anyone else's.

If, on the other hand, you are in a "monogamous" relationship, where one or both partners put others before their partner, or cheat... then I dont think it is better.