I haven't tried the Evod heads, but they're suppose to have a tighter draw, so perhaps they don't rinse as cleanly as the Protank heads do. I've cleaned out my 2 tanks twice now, and I don't have any problems with bad or old flavors (not after a few primer puffs).
The only problems I had, was the first tankful leaked and gurgled a bit, but that was "new user syndrome" of not using it properly. Afterwards, it's all been good. And on my MVP, I can crank up the volts and get a nice warm vape.