So I’m in an argument with my friend, he swears that Harbour will “replace” Viper, and I disagree as I don’t believe Harbour is will be as useful as Viper… What are your thoughts on this?

The better your aim is, the higher the impact mental has on your aim/consistency. At the top of the pro level, with aimers like ScreaM, TenZ, Aproto, I would make an uneducated guess that aim is somewhere from 75-90% mental. Your confidence...