I have 5 Russian 91% Kayfuns, 4 are on ProVaris, and 1 gets shared between anything else I'm using. Add another half dozen Kayfuns in the retired equipment box.
Don't know the cause, but every brand I've used except the Russian starts to develop a nasty metallic taste after a couple of days. The only difference I've found is the Russian is 316 stainless.
The EHPros wick well, and flow a lot of air. They're the only alternative to a Russian I'd consider for taking lung hits.
Have had wicking issues with some of the other clones (Hcigars, Tobeco), and I really don't see what all the fuss is about with SvoeMestos. The newer SvoeMesto Kayfun Lite Plus v2 has a really thin drip tip, plus the airflow is very restrictive. Wide open, it made me feel like an aardvark with a 12" snout going after ants that are 2 feet down in a hole.
I'll take a Kayfun over anything else I've tried for an all day general use vape.