Theatre and film certificates

After watching the brilliant plays Sulari fuq Strada Stretta at the Manoel Theatre and Laughing Wild at St James Cavalier I was bewildered as to why both were certified 18, whereas a huge number of films at the cinema or on TV which are rated at 16 or 12 have more disturbing storylines or images. It was welcoming to see that Sulari fuq Strada Stretta was shown after 35 years to three full houses.

I wonder if anyone from the censorship board can enlighten me on the procedures taken to rate films. Is a Maltese breast more offensive than an American one?