"The ones" or "those"?

They're both grammatically and semantically correct. They differ in style and register.

"..ghettos, such as the ones found..." is verbose: two words versus
"..ghettos, such as those found..." one word.

You'll find both styles in formal academic prose and in informal prose. I prefer the second style and would make the same change were I editing a sentence with the first string in it.

I'm not sure which would occur more often in speech. I tend to speak the way I write (formal, generally grammatical correct, and, I've been told, in difficult vocabulary). Most people write like they speak, though.

There's no rule that forbids anyone from using the ones when talking about people. E.g.:

I generally like girls in their late teens and early twenties, but the ones who belong to Chi Omega Tau are too poor to consider for marriage, the ones who belong to Phi Phi Phi, too intelligent to consider for a fun date, and the ones who belong to Zeta Beta Gamma, too muscular to consider for tennis opponents.

Here's a blog titled The Ones to Watch. It's all about people, not videos or trains or enemy planes.