I'm a righty and proud of it! I hated it as a little girl because my left handed Uncle joked around by saying left handed's are smarter. The truth is it doesn't matter as long as you can write. As for why I like being a righty, I am happy that my writing wont smear as I write it! LOL
It depends on what activity it is.. I'm right-handed for some, left-handed for others. For writing though I'm right-handed, so I just say that so spare confusion. xD
Proud Lefty, although strangely, no-one on either side of my family has been left-handed for generations.
Pro's of being left handed? It's a bit different, 4 out of the last 5 presidents were left handed (Bush Jnr was right handed) and we're often richer and smarter
Downsides are that since the world is made for right handed people (we don't realise, but even things like cutlery, doors, all sorts of random things) we find life harder than our right-handed counterparts (although we don't realise this) and we die earlier. And of course, it is super annoying when notebook spirals get in our way and our writing turns into one big smudge!