Publishing, multiple small topics vs one large topic, at the same rate

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I'm trying to understand if there is any computational difference that comes into play if I publish on a large rostopic (custom and combines all the small topics) vs. publishing multiple smaller topics.

For instance, I want to publish Battery State, Sensor Readings, Odometry, etc. (all at the same rate). Will there be a difference in the computation if I publish them individually vs. one single custom message that combines them all?

Or since the topic is that not large like an image/point cloud, it doesn't really matter?

System config: Raspberry pi 3, with kinetic, publishing topics at 1000Hz.

Thank you