With the ones that require an internet connection, their can be a bit of delay? As the speech is sent to the companies server, processed and sent back. So that you need to have a good internet connection.
Also with Dragon, it it has a 'training' element. To teach it to recognise how one speaks. Which is a bit of nuisance to start with, but results in more accuracy. One way to do this, is to download a page of the 42 Phonemes, which usually have multiple words using those phonemes. Those words can be used, to teach it how one pronounces each phoneme in words. This can also overcome speech difficulties, as long as one is consistent in the way they produce sounds.
It can also adapt to the change in a child's voice, as they grow.
One other important thing with Dragon, is that the Training is saved as a separate file.