Pro's-If you like it, then that's really your preference. I personally prefer short manes in 4 out of 5 cases.
Don't have to cut, and pull, and keep it straight and neat all the time.
More weighted down so, it'll lay flatter.
Con's-More mane to take care of
At a show of higher level, you likely could be looked down upon for it. At a smaller show, the only place short manes really, honestly matter would be in a halter class.
I mean if I were judging WP, I wouldn't count off for a long mane, but some judges may.
"You're just as sane as I am."~Luna Lovegood.