I voted on the side, but that doesn't really match how I wear my sporran belts.

The buckle for my sporran belts tend to be to the left side of my sporran. I do this as I tend to take off my sorran when I am inside the house, and put it on again as I go out. Placing the buckle on the side, makes it faster to put the sporran on, and I don't really worry about how it looks, but I don't think it looks bad.

I always wear a kilt belt, and after I am dressed for the day, the sporran belt is on there too. So, when I am inside, I would have a kilt belt on and an empty sporran belt.

I only vary from this with the dress chain belts that I use for evening attire. Then they buckle in the back, as that is the way that they are designed or made.