It's actually very difficult to tell from those particular pictures - they could be either / or as regards to Singapura or Burmilla. Obviously if they've come with papers, then the breed number will let you know what sort of cats they are, but otherwise, it might not be so straightforward.
However, there is a definite and distinct size difference between Singapuras and Burmillas. A Singapura is a very small and petite cat (around six month kitten size), whereas a Burmilla is a medium-sized (think average adult mog) cat.
Hope this helps.
