I've only used the Sigelei kick just for the sake of trying it and pretty much instantly wanted to get rid of it. I'd rather just have a pure mech and vape above the wattage it supports most of the time. I haven't used a real kick, but I'm pretty sure the Sigelei is lower quality. The numbers also aren't labelled on the dial, which is a tad annoying and the first thing I noticed is that I could hear the rattlesnake noise from the PWM at a lower frequency like a lot of cheap VV/VW devices.
Personally my general opinion is that if you want the original, it's generally always higher quality, but if you're on a budget and want to try something out, the clones generally work almost as well.
There's also the Kick 2, which is essentially the same with some minor improvements.