Everyone has their own opinions about mice (see the 1000's of flame war threads on mice

)
It comes down to you.
Yes,
you.
Best thing to do is go into a Brick & Mortar store like a Best Buy, and actually put your paws on the mice, see how they feel.
I've used a lot of mice, and there's just a huge difference between the ergonomics, how they feel, and how your hand feels after an hours long gaming session. Get a mouse that doesn't fit well with your style of holding & using a mouse and you'll start to notice pain and discomfort in your hand and wrist. not fun.
Short video on the different styles of holding a mouse:
[ame]http://www.youtube.com/watch?v=RqSGFQIcU_o[/ame]
Not the greatest video, but it gives you an idea. Try to identify your style, and that'll help you find a mouse that better suits you.
Also, how big are your hands? Large? Small?
I have HUGE hands: seriously, I can palm a basketball without even trying to stretch my hands (I'm over 6' tall, and have long gorilla arms, too :O )
I tried using a Logitech G9 mouse once, but that mouse is so tiny it was like I could only get a few fingers on it at once.
Logitech G9
The Logoitech G500 was ok, but the Wheel was a total failure for me. I remember having that mouse when L4D was still in it's height of popularity; a common game mouse necessity was changing weapons with your mouse wheel, and you needed to 'click' the mouse wheel to select a weapon; unfortunately, the G500 mouse wheel is so uncontrollably free-spinning and almost impossible to click without moving the wheel again, it made L4D kinda hard. Other than the wheel, I really didn't like the placement of the side buttons, and the texture was like sandpaper.
Logitech G500
A larger line of mice (like what I'm using now) is the Microsoft Sidewinder series. Decent mice, feels nice (IF you have big hands). These mice feel, I dunno, like their built industrial strength strong? Overall mostly hard-plastic feels like it'll last, but not as comfortable to hold as the Razer Deathadder.
Microsoft Sidewinder X5
If you need a wireless gaming mouse:
MIcrosoft Sidewinder X8
The Razer Deathader 3G (I've had that one, too) is a good mouse. My only complaint about that mouse was the sensor: it had to be used on certain surfaces, and white surfaces wasn't one of them. Since my desk is white, it wasn't a good fit for me. I loved the way it felt, and (when used on a mouse-pad) it had great response and tracking.
Razer Deathadder 3G
The Razer Lachesis has a better laser sensor, but a very, very different ergonomics. Might be a good mouse if you have a finger-tip control style. It's very low to the ground, and wide in the front. If the idea of having a mouse that doesn't have that 'arch' to rest your palm on sounds tempting, this is the mouse for you:
Razer Lachesis
The Razer Mamba (a great mouse) is essentially a Razer Deathadder with a better laser sensor, wireless, and offers DPI switching. Kinda pricey though, but worth a look if you can afford it:
Razer Mamba
Sorry, but I don't have any experience with the Steel Series of mice.
If I was on a budget, and wanted a good, cheap mouse used primarily for gaming, I'd consider the Razer Deathadder and the Microsoft Sidewinder X5.
Remember, the Razer Deathadder does NOT offer on-the-fly DPI switching (practically every other gaming mouse does). Instead, you can map (via the Razer software) sensitivity changing to one of the buttons. (I mapped mine to the mouse 'click' button) Click the mouse wheel, and scroll the wheel up/down to adjust, and click again to set it. Not as nice as actual DPI switching, but it gets the job done. The Deathadder feels tremendously better to hold (the texture of that mouse is great) the Razer software is sooooo much better than the Microsoft software (if you want to remap buttons, macros, etc, Razer is far superior to Microsoft).
The Microsoft X5 is overall ok, but it might be too big for some people, and it only has a 2000DPI max sensor.