In my experience Grok 4.5 codes at Opus 4.8 level, and being much faster as cheaper, I can just ask it to do self-review and the final reviewed code is _better_ than Opus 4.8 for the same time/budget.

But Opus 5/4.8 was better for non-code architecture discussions and general intelligence. However, for the cost, I'd use GPT 5.6 Sol and get much better results. Interestingly, Sol is not great for coding - slow and overengineer stuff if you're not explicit.

My go-to workflow was Sol for planning and Grok for building. But my in my first tests with Grok 4.6, I found it quite good and I'll start using it for both; assuming it's as good at is shows at benchmarks it's unbeatable at cost/time.