There are a lot of questions on http://scifi.stackexchange.com which relate to Sci Fi movies and TV shows.
It seems like this site would be the place to ask those questions.
Is there a difference between asking it here vs. asking it at scifi?
It would be nearly impossible to keep the scope of all SE sites mutually exclusive, and SciFi and Literature are clearly sites which overlap with us. This issue is seen across SE.
Partially it comes down to personal preference. You might feel more comfortable in one site or another. SciFi is a more established site, has a great community of followers so undoubtedly there are going to be questions there that would also be suitable here, but that is the site they are happiest posting in.
You might also prefer a perspective of a movie goer or sci-fi addict, so would choose one site or another. For instance you are probably going to get more responses from SciFi if the question is about underlying SciFi themes or ideas, or links to the book that a movie is adapted from (though this is also often covered here). Here the perspective is going to be more about the movie, even if there is prior media such as books or comics.
It is generally discouraged to migrate questions between sites purely to try to get them into the (subjective) best site. If it is on-topic for the site it is generally left there. The SciFi mods are aware of us, and do migrate questions that clearly would be better handled here, such as a lack of SciFi content to the question.