In my experience, YouTube’s is much more influenced by the latest videos a user has watched. It’s pretty much always "more of the same".

TikTok seems to manage to more quickly identify users’ interests and surface content based on more signals, aggregated over a longer period of time, without relying as much on conscious users’ actions (ie "follow / subscribe"), producing a wider diversity of recommendations.

There’s also the odd suggestion every now and then, probably used to gauge a user’s interest in a different category.