If you are getting the chin for pet only - and don't care about show/breeding quality... Still, the only advantage I believe there is to buying kits is that, in my experience, they are much easier to pair up with cagemates than adults are. Since they are still young they quite often remain in their submissive role and do not challenge another chin for dominance. Of course, this is not always the case, but as a breeder who consolidates cage space from time to time, I find it much easier to make cagemates of kits 6-7 months and younger than those older. However, I break up pairs often as well, as they sell or as I prepare them for show, so I cannot say if dominance becomes an issue later as they get older.
I do not believe kits can be "tamed." The idea that it is better to buy a kit so you can bond with it/tame it is, IMO, false. Most kits are far too energetic to be interested in people. Yes, they will eventually come around as their hormones settle down, but I doubt it's because you've played with/handled it since it was young. Adults in general are less spastic and, since they can live 15-20 years, there's still PLENTY of time to bond with them.