Cross trainer or Air walker ?

Which is better for toning up ? and which parts of the body are they best for ?

The cross trainer is the better of the two but it will only work on upper thighs and upper body. It is a good cardio-vascular exercise also. Why dont you go to your local sports centre and they should have a fitness coach who will assess you current fitness level, instruct you how to use the equipment correctly and give you a training programme to meet your requirements.
I hope this helps.

I would suggest the cross trainer, although if you already have dumbells and can discipline yourself to swing your arms with purpose and not just fling them around the air-walker can be good also.

The main thing with both machines is that they provide great fat burning cardio workouts. This means the fat should fall from all over the body as you cannot spot reduce fat. Your muscles in the lower body should grow either 'tighter' or larger depending on what you define it as and what you do. Combine this with some Muscular Strength work and you can get great results.

You could always try jogging or skipping as this is cheaper and just as effective! :)