If your basing it on stats, then Unfezant has better Attack, Defense, and Hp. But Swanna has better Sp. attack, Sp. Defense, and slightly better Speed. Swanna may have better moves, but remember that it has a 4x weakness to electric types due to the Water/Flying combination.
So in all, I would go with a female Unfezant, because they only have a 2x weakness to electric types, and because female Unfezants have better stats compared to Male Unfezants.
Hope this helps!