I think I'd go for "who" (and I'm from Manchester, so just watch yer back young Zimmers) but, in more linguistic terms, it is less straightforward. It all depends on how you view the matter conceptually. It's also amazing how arbitrary the accepted rules of grammar are. Many of the things which are quoted e.g. "don't split infinitives" stem from an eighteenth century attempt to impose some of the rules of Latin onto English, simply because of the daft notion that it was felt that Latin was somehow superior. Now just use common sense: what is going to be superior, something greasy from the Med or something clean, upright and Anglo-Saxon from the more temperate north?
To be slightly less contentious about it, I would recommend a read of The Language Instinct by Steven Pinker, if you are interested in this kind of thing.