Hi, I'm coming with input a little late but I hope this helps at least one person reading this wall of text.
I used to be competitive CS player since 1.6 was launched and before that I used to play for fun since 1.1. Had my days on source and stopped because of college and work.
By the way, I'm Brazilian, and I had the opportunity to play with highly known players like the guys from MiBr (made in brazil) and fG (fire gaming) on the 1.6, as well as vsONE, sXgaming and other great teams from Brazil.
First of all, in a short answer, the best option for you is what feels natural in your hands and has a quality sensor.
By quality sensor I mean the basic thing we used to say: if you perform a fast movement and the cursor "bugs" (doesn't respond, make random movements and end up in the sky/ground) it's not a quality sensor. If you do perform a fast movement and the cursor follows, you are good to go.
Furthermore, the funny thing is I only met one or two guys that were hardware enthusiasts like me and not even they knew all about mouses. By this I mean that those players on MIBR or fG that won the world cup had no idea what mouse prediction was, didn't care for laser or optic sensor, double sensor, on the fly sens, driver sweets, firmware updates, etc. All we did was buy a mouse, get used to it and use the same sens always on windows, in-game and DPI settings all of our life.
By the way, I got used to the razer copperhead, and one of my teammates used the krait (I think f0rest also used the krait, until he got other tons of sponsors), which aren't even sold anymore and if I go back to competitive gaming I will have to get used to another mouse.
The guys in MiBr all use the simple microsoft intelimouse 1.1. I asked them why, they said it was because they got used to it because it was the mouse available on the cyber-cafe they used to play on their early days.
All in all, I hope this helps you and anybody looking to get serious in any kind of gaming. Forget all the specs that can even sound like marketing gimmick for many pro players and look for a mouse that should fit your hand, feels natural, and then just use the same settings for your whole life.
here is a picture of nak from mibr and his mouse (IMO the most skilled player on the team). He played for us on CS:S for a month when one of our teamates left the team and we had to find somebody else.
You can google for images of mibr and see that they use the simple intelimouse 1.1 Edited by EduFurtado - 1/29/12 at 3:15pm