I think if you're right handed, you should fight orthodox.
I understand that being converted is the new rave these days, and a lot of VERY good fighters have been successful w/ it...e.g. Winky Wright, Oscar De La Hoya, Chad Dawson, Nonito Donaire, etc...
My problem with that is this. When you're in a hole, and down a whole lot of rounds, you need to rely on a game changing hook to knock a guy out.
Like after Paul Williams shut Winky Wright out for eight rounds, I knew it was over. No way was Wright going to land a hook and hurt Williams (granted P-Will had a great chin and Winky can't punch).
Overall, I think you should fight out of the stance which is more comfortable for you and where your coordination/balance is the best.
As I said though, when you're down on points and need a game changing punch, lining up a right hand (or left if you're a southpaw) is the best way to do it. If Tommy Hearns or Kelly Pavlik were southpaws, would they have been nearly as effective?
The answer is no.
Converted southpaw is how I fight, I jab with the right hand instead of the left,and throw straight lefts instead of a traditional jab/right cross. Since my lead jab is also my power shot it allows me to hook off the jab with great leverage and success. I throw a baseball right handed but shoot with a hockey stick, bow and sling shot left handed. I can swing a bat and shoot a gun either lefty or righty but feel more like a natural right hander than a souithpaw and sign my name with my right hand. The southpaw stance that a converted conventional fighter uses seems, for me anyway to add something to my effectiveness as a boxer. It has worked for a few world class fighters over the years but not many.
In football (soccer to yanks) its always said that a good player should be comfortable using both feet.
I've always been of the view fighters should, from an early age,be trained to switch stance and be comfortable either way so they have more options
I like to fight unorthodox. In fights I will constantly change from southpaw to orthodox, change the angles of my punches and will use my jab from both sides to set up my power shots. My favorite combination is jab, cross, hook (to the body)
What's your favorite