Choose a bike with a smooth pedaling motion. Make sure the bike is easy to assemble. Look for bikes with monitors that display time, speed, distance, workload and calories burned. As one step goes down the other automatically goes up. These are usually awkward to use and cheaply made.
Steps move independent of each other.
These machines are better quality than the other model. Use weighted flywheels with fan blades to provide resistance. Chain or cable should provide a smooth rowing motion. As one foot pad moves forward, the other automatically moves backward. Usually less costly.