“which is best cad software ?, i am currently using creo 1.0”
I’ll vote for Solid Works – easy to learn, very popular, accurate and versatile.
The one you can afford :(
It depends on what you're using it for. Every Cad Package has it's own little niche in specific markets. HUGE QUESTION!!!! but the BEST question!!!!! Think of it like shopping for a car. How much are you going to spend? How well, will it get you from point "A" to point "B" with the most comfort in the ride? How expensive -or- hard is it to fix and maintain? What's it going to cost to run it annually?
If Easy is your objective, Use CATIA.
I would recommend Solidworks, simply because it is capable of almost any task you would need a CAD software for, very complete and widely used. The only downside i foresee is the price of a license.