Generally, users tend to respond better to "just in time" education when getting accustomed to something. App start screens, whether they're onboarding or otherwise, tend to cause drop-offs.
Authors like Luke Wroblewski and Josh Clark write about this from time to time. There's a great example in this post.
A couple quick quotes:
Most people (sometimes over 90%) skip over intro tours as quickly as possible and those that don’t rarely remember what they were supposed to learn. Both these issues stem from that fact that introductory tours show up before you ever get a chance to use an application.
Some mobile apps aim to get around this by overlaying their tour on top of the actual interface design but even with a picture of the interface present, people lack the experience to know which actions will be useful to them and when. And over time they’re likely to forget which interactions are possible in any given app as they switch between them regularly.
It's certainly much harder to design this way than it is to make a quick video or overlay tutorial and stick it at the beginning, but it's far more rewarding for users.
This isn't to say that you shouldn't use tips and messaging to show users how to do things, especially if they're not familiar with the interactions you're presenting to them. It's just to say that the beginning (or in a video) is often not the best place to do it. The goal for which we should strive is always to present what the user needs to know right when they need to know it.
