I don't think there's a difference in the taste of the meat, if that's what you're asking. A&M tend to be big, so they would be close to the jumbos for size.
I have had up to a 90% hatch rate on shipped eggs. I get mine mostly from Myshire Farm or from people I trust from here. Your hatch rate really depends on how well the eggs are packed, how the post office treats them, and your own incubation conditions.