I train both sides, however, prefer to keep an orthodox stance which sets up stronger boxing techniques due to me being right handed. This allows good hand set ups and power roundhouse kicks with the right leg, my more powerful leg, and also allows me to set up my side thrust and front thrust kicks from the front leg, making them quicker and harder to see coming.
In Pai Lum we would often fight with our strong leg in front, which would put me in Southpaw stance with the right leg forward, which is good for strong side kicks, quick roundhouses, hooks, crescent, and ax kick.
I always balance the two when sparring, the key is to know when to switch stance and not do it at close range where it will be easier for your opponent to catch you off guard with a strike or clinch. This is the one critisism I have of some combat sport styles who advocate never switching stance. If done correctly it can mix up your techniques and keep your opponent unknown of what you will throw next. The key is learning how to properly transition between the two.
"The hero and the coward both feel the same thing, but the hero projects his fear onto his opponent while the coward runs. 'Fear'. It's the same thing, but it's what you do with it that matters". -Cus D'Amato