Amtrak business class affords the luxury of roomy reclining padded seats, more legroom, tray tables, and outlets for your computer. They even have some areas where four can sit facing each other with a fold-down conference table. In business class, your seat is reserved and are provided with complimentary beverages.
Coach seats are not reserved for short trips, and even though you pay, you are not guaranteed a seat. If you choose coach and are going on a long journey your seat requires a reservation in advance, and it is secured. Coach does offer a comfortable seat that does recline, has legroom, tray tables, and overhead lighting.
Fares for seating depends upon the time of day, where you are going, and holidays or regular days. The distinction between coach and business is about $30 - $40, and they do have a rewards member program that offers percentages off, which comes in handy if you travel frequently.