IMO both can be easy to use without any problems or very habit forming depending on your personality - I used to be in the "Cannabis isn't addictive" crowd simply because it didn't affect me or my close friends in such a manner but now with a little more experience I find there are a lot of parallels between cannabis and synthetic cannabinoid habits and opiate/opioid habits (something I had not read about until recently is that at least the primary cannabinoids in weed, THC and CBD - seem to be mu opioid receptor positive allosteric modulators, similar to benzodiazepines being PAMs for GABA - which makes sense, there are many parallels between the highs, pain-killing qualities etc - in fact I've even nodded out with stronger synthetic cannabinoids before), albeit the latter builds up much heavier in a shorter space of time - the end results are similar, it's just while it can take months to reach that stage with opiates it can take years with cannabinoids. Sleep issues, nausea, pain, distress etc can all be issues of long term daily use - though it takes a very long time for most individuals and also greatly depends on the amount that's being smoked (taking potency into account) - i.e. someone getting stoned each day might not even have problems but someone smoking heavily all day every day usually does eventually.
With dissociatives there's also a risk of developing a habit but it functions rather differently - while Cannabis tends to have little "pull" to use daily until you've used it for a very long time (if ever - usually for most people they get habits from the fact it's *not* seeming to be habit forming or causing problems from their perspective and they simply use it in too large amounts for too long and then find it's difficult to stop) dissociatives in my (and most peoples it seems) experience can be very moreish, I'm sure you've heard of people describing opiates as the ultimate escape because they can ease all pain both physical and psychological - but what about a drug that can both do that and transport you to another world where you can forget your whole life and be whatever you want, that's Ketamine to me. The allure should be self-explanatory.
I don't find Ketamine to have much in the way of physical symptoms like long term Cannabis use does but it comes with the trade off that it's much more tempting to use it and get sucked up into the hole for a long period of time and forget about your every day life - I know when I was using Ketamine fairly regularly I probably spent more time in the hole than I did in the real world. With long term abuse people also report cognitive decline, problems with speech recognition and communication etc - they tend not to be very severe and mostly unnoticeable, not like say someone who's been eating MDMA every day - but it's still a very real issue and something I think anyone should avoid. There's also the bladder and kidney damage heavy users face.
In short, both are lovely substances and both are safe and useful in moderation but both have consequences with long term heavy use. I think it very much depends on the individual if they'll find either or both becoming a habit for them.
