Safest Route

What is the best route from omaha,neb to fresno,ca is it i-80 or i-40

First thing I would be looking at is the weather. Snow and possible road closures due to the flooding.

Weight of your load is also very critical when you're examining Wyoming. The winds can be nasty this time of year. For an inexperienced driver I40 is likely a little safer, but you can only cut it out so much. It also depends on your company routing, you'll want to check with them too if you want to try changing things.