I'm confused to choosing softwere between solid works and NX 10 which is more useful?

If you are looking for PLM software/ Complex surfacing go for NX, If your use is limited to design, Drafting and assembly Solidworks is best.

This all depends on what you are designing and making. What would you be primarily be using the software for?

This is a professional comparison...
Check it out:
https://www.g2crowd.com/compare/design-to-siemens-nx-vs-solidworks

Really depends on the work you're doing.

If these were my preferences...

Collaborative, large assembly projects?
Top-down assembly?
One package for CAD/CAM/CAE?
The need for Sub-d modeling (Realize Shape module) within a parametric environment?
Synchronous modeling?
Surface models to Class-A modeling tolerances? (If you're looking to primarily model to Class-A, neither option would be my first choice)

NX

For everything else?

SWorks

For Surface Modelling and Complex application NX is Best , For Die Design , Drafting , Assembly work Solidwork is Best and Easy Software.