A lot of content overlap for sure, but there are some differences in the type of content and significant differences in the algorithm / the distribution of content types within one’s feed.

For example, I’ve found that YouTube shorts will identify multiple creators or formats that you engage with and rotate between them, while Instagram reels tends to find one niche you respond to and then bombard you with it.

Regarding comments, shorts will promote shallow observations about the video while reels promotes controversial ones to get one to engage by arguing.