But he is totally right Spanish is more consistent in that respect, because it has a plural article. You can say "son unos perros" as well when you put that sentence in plural.

Of course, that doesn't say anything about the languages in general, there are also things where Spanish is less consistent. E.g. why do we say "la película es buena" but "el día está bueno"? I'm a native Spanish speaker and when asked by foreigners about a rule that would explain that, I've never been able to come up with one.

I'm learning Chinese and my feeling is that it's more consistent than both Spanish and English, things actually tend to make a lot of sense in Chinese. A pity that between the tones and the characters, it's much harder to learn than either of them.