Exactly my experience as well. Like Sonnet can help me in 90% of the cases but there are some specific edge cases where it struggles that o1 can solve in an instant. I kinda hate it because of having to pay for both of them.
I've been using Claude 3.5 over API for about 4 months on $100 of credit. I use it fairly extensively, on mobile and my laptop, and I expected to run out of credit ages ago. However, I am careful to keep chats fairly short as it's long chats that eat up the credit.
So I'd say it depends. For my use case it's about even but the API provides better functionality.