I’m on the $100/month plan. 1-2 prompts in I got my limit on Opus, then I spend most of my coding day on Sonnet.

Whenever I am on Opus, it isn’t obvious it’s writing code that Sonnet can’t. I see a bigger difference between prompts that do vs. do not have “ultrathink” rather than Sonnet/Opus.

Does anyone with more experience have a clear perspective on Sonnet vs Opus? Even on the benchmarks they are about the same.

I am on the Max plan ($100) and quite happy with Opus 4.5 so far. I have decided to go into a self-hackathon mode to work on one of my projects tonight.

I started at 22:30 with 0% usage of the 5-hour limit.

I turned off the thinking mode, hoping that Opus 4.5 usage will last longer. I have two sessions open at the same time to work on two different features. So far so good for the first 2.5 hours. I checked the progress, and it told me that I had used 67% of the 5-hour limit.

So, I switched to Sonnet 4.5 with the hope that I could last until the next 5-hour window. I can clearly see that the quality and speed were a little lower compared with Opus 4.5; I had to provide more instructions.

To my surprise, I hit the limit faster than I expected.

My guess is that Opus 4.5 follows instructions better, leading to fewer retries and much fewer tokens spent.

So, in the end, maybe Opus 4.5 is even cheaper than Sonnet 4.5.

I work in quantitative finance, so most of my programming revolves around building financial tools that detect and exploit market anomalies. The coding I do is highly theoretical and often based on insights from academic finance research.

I’m currently exploring different models to help me reason through and validate my approaches. Does anyone have experience using Opus 4 of Sonnet 4 for this kind of work? I’m trying to figure out what is the best fit for my use case.