It makes people behave very strangely, whereas when I see people on coke and having tried it once myself, it doesn't make such a huge difference to the user's functionality.
Yes, you're right that in the short term, K has a much more extreme effect than coke. You might not realise the reason someone was eing a self obsessed arse was because they'd taken a load of coke. And, it's harder to ignore someone so out of it they have no idea where they are or what they're doing.
I guess, lots of people take a little bit of coke and don't see it as a big deal. I suppose if they don't take it that often, it could well be seen as less extreme than K. However coke isn't a nice drug IMO.
If we're talking about regular use, I'm much more wary of coke than K.
It tends to make people arrogant and self obsessed; it's much more addictive than K and the underworld connected to it is much darker. Addicts do desperate things for coke, especially if you think about coke in crack form - thousands of women prostitute themselves for crack. People beg, steal and mug others to get enough money for crack. Women are often raped in crack houses. Coke / crack is controlled by international criminal gangs and is destroying the economies of many countries.
K, on the other hand, is a pharmaceutical drug that's produced for medicinal use. Last time I did any research on this (disclaimer - things may be different now), it wasn't controlled by criminal gangs in the same way coke is. It was acquired in relatively small amounts by dealers direct from pharmaceutical sources, then sold on to users. More of a cottage industry, if you like, than coke. Problem users don't prostitute themselves for K, or beat people up to get money for it. If you move a user out of the world they take K in, they're fine without it.
While users are much more out of it when on K than coke, it's not nearly as addictive or dangerous. It doesn't turn people into absolute low lifes IMO, although it does make regular users very boring.