I was a bit suspicious when information began to surface that the new z-Enemy miner was about 10% faster than other miners. I had been happy with Raven Miner which had been giving me an average hash rate of 150-160 MHz over the last week.
I downloaded z-Enemy and started running it 18 hours ago. Over this time, my MHz has jumped to and held steady at 200-205 MHz (20-25% faster for me). I'm not sure what causes one miner to be more efficient than another, but it is certain to me that my informal observations concerning the hash-rate of the two miners are noticeably different.
It's always important to get the latest version of mining software as it will make the mining more efficient. I've been mining for more than a year now and its a good practice to use latest mining software whenever devs release new ones. Gives bigger profit.