EC1 for big hands, ec2 for small hands. there are 2 version in EC series. In evo version there is no prediction, whereas, there was a bit of prediction on normal EC series. evo mouse are awesome, I used once, but I personally like little bit of prediction. So normal version are best for me. According to the size of my hand, EC2 is the best. Till now there are not even a single bug, like double click, scroll problem, etc. Zowie mouse are best, you will be amazed by the performance of these mouses. Me coming from Kinzu v1 and Deathadder, after using those mouse for more than like 4 or 4.5yrs, it took only 1-2 weeks to set my hands on ec2.