There are advantages to each style, and when you train both you can benefit more due to the differences. If you start training sumo and realize that you are in fact stronger that way then that will be an important breakthrough. I was a conventional deadlifter for a long time, and eventually was able to switch styles and make substantial progress past my previous plateau in the conventional style. In the end my conventional went up a ton from the weights I could handle pulling sumo, so sumo made both styles increase for me.
As far as what the differences are...
sumo, if your hips are flexible, allows you to use more lower body strength and less low back strength. If you have very strong hips and can adapt a relatively wide stance, you can drastically improve the ROM of the lift.
But in the end it just comes down to feel, and I always recommend training both styles. That's the best of both worlds.