I came across two bikes that I don't know which one would be better - surly long haul trucker and kona rova al. They both ride are great bike but they make out of different materials so I'm not sure which one would be better.
First, don't obsess over frame materials. Despite the hype (and there's a lot of that!), the shock absorption is in the tires instead of the frame. Aluminum won't rust, but if you rust out a bike riding across America, you're going too slow!
Second, pick the one that fits you best and is the most fun to ride. If you like riding your bike, you are more likely to ride your bike, and the cost benefit ratio improves the more you ride.
Finally, the LHT has lower gears you'll appreciate in VA, KY, MO, CO, WY, MT, ID, and OR. (Not much difference in Kansas or Illinois.) If they both fit and ride alike, get the LHT.