Realistically you should compare Amtrak to air travel to see if it competes on price, convenience, and scheduling. One train a day usually won't do the job. Four trains a day might, and only if it is relatively short distances [under 250 miles]. I rarely take the train for business, unless I am in the Northeast. Even between Boston and NYC it is questionable. The train always wins between NYC Philadelphia and Washington DC. But from Denver, I doubt it beats the plane.