The work I do cannot fit in 256k so it was just relearning the same things over and over again while making zero progress. AFAIK the 1M burns tokens at twice the rate but I use Sol on medium as the work I'm doing now needs more memory than it needs intelligence and it's working great. I use Opus 5.5 for the stuff that needs stronger intelligence.
That has not been my experience after bumping it up to 1M. I do run a lot of agents in parallel ~10-16 and I actively babysit them so perhaps I'm just used to reminding the agents with things I've already told them. But I don't notice much of a difference between Sol 6.1 1M and Opus 5.5 1M