It's a matter of preference. If you can piece it with one seam and don't mind how it looks, go for it! I will often use leftover blocks or strips to divide my 2 pieces, especially if it's a large print that I don't want to match. Plus it ads interest.
Most of the time I run a seam down the middle. I use my quilts frequently and never noticed any stress on a center seam. I think if you quilt it enough it shouldn't be an issue. There are a lot of people who disagree with this, but that's how I often do it. :)