Chitowndl offers another way to decide which style might be best for you:
A lot depends on height, arm length, belly size, and back strength compared to hip strength... Go with the feel and see how you do. You can train to be strong at both, but this is something you will figure out in time.
BangVader thinks if one can, they should deadlift conventional:
I think if you are a wide squatter you will be better at sumo were if you were a close squatter you would be better at conv.
I think if anyone can deadlift conventional...they should...depending on your bodytype. I see it a lot and I think the conventional has more potential for pulling big weights. There are a lot more advantageos leverages with conventional.
Another point is the training aspect. A sumo DLer's weakpoint is almost always from the floor. Conventional is much higher in the lift. You can utilize a lot more training tools like bands, chains, and lockouts to help. I'm not saying you can't use those as a sumo guy. Nor am I saying you can't do other thinkgs to help you off the floor (blocks). I just think there are advantages for a conventional DLer.
Some of the posters think that it's all about experimenting with each and seeing which your body is most comfortable with. However edoggpower responds with an interesting take on that:
I think the only exeption is if you are very short, with short arms and a big belly.
Sometimes you feel comfortable in a false state. When you begin deadlifting you will pull more where you have naturally grown to be stronger via sports, working, or whatever. Sometimes you have to train both ways to get other body parts fired up and stronger and then see where your more comfortable.