One thing I find consistent about most of these posts by people who advocate owning pet primates is that they always have a young primate.
What you have at 10 or 11 months is nothing like what you will have at 5 or 10 years. This isn't just an opinion, it's a fact. In the 20 years I worked at a zoo, I saw many monkeys (as well as other primates) grow from cute and adorable to aggressive and moody. I've even had young woollies in my home for short periods. They are killer cute, no argument. As adults however, no way I would ever get within reach of an animal with large sharp canines, the maturity of two year old and the single, mindless drive to physically dominate every single being it comes across (particularly it's keepers or owner).
The telling thing for me is the fact that over the decades, I've seen bird keepers who owned whole aviaries at home, reptile keepers that had huge collections of herps, hoofstock keepers that even owned things like camels and zebras. However, I've NEVER seen a primate keeper that wanted to own adult primates as pets. ...and there is a reason why. They don't make good pets as adults.
To quote exoticpetvet.net:
"Hand-raised, bottle-fed babies are quite charming, but with the onset of sexual maturity, they become unpredictable, aggressive and dangerous to humans - including their owners. Consequently, people should be discouraged from keeping them as pets.
If a client is set on owning a callitrichid, however, he or she should be steered toward a tamarin instead of a marmoset, as they tend to have more stable personalities as adults and are not as aggressive or unpredictable."
There are exceptions to every rule. I'm even sure that there are some people out there that have the money, time and dedication to keep them responsibly and safely. Thre is also the chance you'll hit the lottery next time you play.
But if you search the net, the news and the scientific literature you'll find far, far, far more examples of bad outcomes than good ones when it comes to owning pet primates.