I don't really know if Expressmail is checked out more than Priority or Regualar mail BUT there is a lot less of it than the others. Also, the Post Office handles it more carefully because it is a big money maker for them and they really treat it as such. I myself would think Priority Mail is a better route. There is a load of it so it could not be singled out and it is treated with high priority as it too is a cash cow for the USPS.
Otis