Your question is loaded and forces me into a false premise: I.e. we need "external experience" at a position.
Given that choice, sure Bonnuci certainly is a household name thatcomes to mind. And I'm not surprised many list him. I just don't think he's worth the money. Especially because there are many as good (or in my opinion) better who are way cheaper.
And if you ask me for the name of one right now who I think will be better for Pep's squad, philosophy and City's style? Vlad Chiriches at Napoli. Yup same guy who couldn't make the grade at Spurs a few years back.
Bit right now he is who I'd rather if I wanted an experienced CB. He is a better passer than Bonucci (shocking I know, folks make it sound like Bonnuci was the best thing since sliced bread) better tackler, harder worker too. Not to mention, he'll be 28 when he gets here (you know, the age Pep specifically mentioned :p)
But that's only if you force me to choose an experienced defender, which by the way I wouldn't seeing as we have Kompany, Otamendi, and Kolarov. All above, at it approaching 30. And chuck full of experience.
If I were to go for any CB at all it would be Marqhuinos at PSG. Who we should have probably nabbed when he wasn't getting playing time.
So in short, I'll take Vlad and Marqhuinos over Bonnuci every day of the week.