The longer the dissolve, the smoother the transition. Generally, when I have stills moving into moving video, I’ll do a 1 second dissolve that gives me a half second crossfade to each side — unless I need to start the transition early or late because there is not enough material on either end.
Short dissolves get you in and out of jams but lots of material that is moving benefits from longer dissolve transitions.
One thing I tell people who are shooting material is that most of the movement happens in the edit. You make a film or program move by cutting from one shot to another so that the viewer does not get bored with just one stable shot (emphasis on the word stable here because stable shots give you the best means by which you can tell a story).
But if you are doing another Blair Witch Project, you want moving shots with cuts between them. That exaggerates the nature of the movement (usually termed “visual whiplash”).
In your case, you are looking for something more sedate. Assuming your video is color-corrected and that everything is just fine, any abrupt transition will benefit from a dissolve, a dip to black, a dip to color or a similar crossfade transition.
What if there were no hypothetical questions?