which mouse do you prefer  

i am using optical mouse

You are going to run into a little bit of a problem with what you said. You can get a good wireless mouse, but you do get what you pay for in this department. I have the Logitech MX1000 and it is by far the best mouse I have ever owned with a tiltwheel, 7-buttons and awesome sensitivity. But, I payed almost $100 for it (it is a little cheaper now).

It was said above that the sensetivty sucks, and that batteries are a pain. This is simply not true IF you buy a good mouse. My mouse has a rechargeable battery that lasts for a full week without recharging (just throw it on the base for a couple hours when it does). And the sensitivity is great!

When you look at costs, a $50-$70 wireless mouse will have the performance equivalence to roughly a $30-$40 wired mouse - you have to realize you are paying for more technology in the wireless mouse.

So, I wouldn't recommend buying a cheap wireless mouse. If that is your price range, go with wired. If you really want a wireless mouse, spend a little more money.

This one looks like it might be decent for around $40: