I've heard about this lemo how does this exel over the kayfun? They virtually look the same...
That would depend on what's important to you in a tank setup. You build them the same, but a lot of similarities end there.
If you like a really airy draw, hands down, go with Lemo. The amount of airflow I can get out of mine is almost ridiculous; I usually close it up some.
My Kayfuns have a clear plastic piece in the middle so you can see your juice level, but not all juices are good for plastic tanks (tank crackers, as they're called). Lemo has a glass tank so you can use any liquid in it and see your juice level. The alternative with the Kayfun is to put the stainless middle piece on - now you can use any juice you want but you can't see it. Your other option with the Kayfun is to buy the quartz nano kit, but now you're spending $$ on it again and it's only held on with O-rings.
Kayfuns can have leaking issues. Some people never have a problem with this, but many do. They can be quirky. Lemo's don't leak.
Lemo has a slightly larger build deck and a noticeably larger air flow hole under the coil than the Kayfun does.
The downside to the Lemo is that there is no optional stainless center tank or sleeve and the glass is on the thin side. While it's great when I'm home, I'm a little leary traveling with it. The Kayfun is a bit sturdier and heavier overall. I keep the stainless middle on the Kayfun because I know if/when I knock it over, it will likely survive. I don't have that option with the Lemo.