You should always choose video-producing services that can effectively match your creative brief requirements. By checking their portfolio you can see if their video edits match your style and vision you want to portray.
To check their skills, look at their past video examples. This will give you a good idea about the quality of work they have delivered to their clients previously. To understand how well they match your style, you can even ask them to work on a paid test project. It’s a great way to check their skills and not have to hire fully until you’re confident in what they can provide.