YOU'VE NEVER SEEN A HWEI LIKE THIS 

It also feels like antiheal is a joke these days. If a champ has botrk/ bt/ravenous then antiheal will somewhat work, but against champs with innate healing it's worthless IMO

I play both, personally i prefer vel'koz, ir way harder but has more slows and zoning that xerath, xerath is easier to play and has more damage. The good thing of vel'koz is the burst of the passive and the true damage, it looks dope hit a Q R, its my favorite for style points

Maybe you can formulate a better question, but what do you want to do powerfully? Even a newbie will tell you the obvious, if it's about the obvious. Velkoz is difficult to play due to the specificity of positioning. Zeret surprises the enemy less in the lane, and it is also more difficult for him to fight if the enemy has broken the distance, the reason for the "E" mechanic. It is easier to dominate Zeret, which means that he lags behind more, this is the "snowball rule", Velkoz has a weaker snowball, but also lags behind less. Velkoz does more in teamfights.