It would be interesting to compare the results for the same person but from different genetic testing services.

I watched a television programme a while ago about a similar service for dog owners to find out the background of their pets. They had to send in a sample along with a photograph of the dog. And guess what - the results came back with the dog's ancestry closely matching the photograph of the dog. Even when they sent the sample with a photograph of a very different dog.
And even when they sent a photograph of a dog with a DNA sample from the programme's presenter.