Is the cross trainer or the elliptical trainer more effective?

What is the difference between a cross trainer and a elliptical trainer?

How should I maintain my cross trainer?

3603 Cross Rower 2.5

4131 Cross Stepper

4131 Cross Stepper

3602 Cardio Strider 3.1

4125 Crosstech XTR

What can I train with a rowing machine?

4110 Crosstech XTR BT 23

66426 Cross Jump

4866 Cardio XT9 BT

4862 Cardio XT6 BT

Do I need to maintain the ergometer? Do the moving parts inside wear out?

4111 Crossfly XTR BT 23