I've been using 5.3 since they initially announced it and my gut feel is that it's not as good as 5.2 for agentic tasks. I'm still using it - I don't think it's bad. I'm just not convinced it's better.
idk i think that i spend significant tokens with both to be able to tell 5.3 is way better overall.
https://kommodo.ai/i/IFSUUQYT522uZXWvePZ1
it still fells stupid sometimes and it is benchmaxxed for sure. but its good enough that im building all the hobby projects with it.
I have had the opposite where I felt 5.3 as a stronger model than 5.2. Its feels way more in tune with my code, and does more nuanced edits. Though I do handhold my models a lot, so might fall outside the agentic term.