The "best" mech is very subjective. There are a lot of variables involved, so you will need to research and decide what is "best" for you. I have several authentic mods and a couple of clones, and I use them all. If they didn't work for me I'd get rid of them.
Edit to add: My two clones are an Hcigar Nemesis and a copper Vanilla mod from 101Vape. Both have the switch magnet upgrade from FatDaddy vapes and both work fantastic. The button on the Vanilla mod was a bit finicky at first but after adding the magnets and adjusting the pins it works great and hits hard. A solid value for 30 bucks, IMO. Of my authentic mods, my Super T mods probably are my favorites for dripping, with my Atmizoo Dingo coming in very close second. For a bottom feeder, nothing beats my Reos.
As far as RDAs, I would have to agree with a few of the other posters here that the Igos are a fantastic value. I bought several Igo L's and a couple Igo W's and IMO the are both better than a lot of clone RDAs that I have owned/used. In fact, after buying and owning the Igos I won't spend 50-100 bucks on any other "authentic" RDA. Just my opinion, and what works for me.