I'm coming around on this too. deepseek-v4-flash is impressive.
I've seen people outside Google favoring flash Gemini models over the Pro.
There are also some benchmarks where flash models have higher scores, so yes, apparently speed does matter.
I see a lot of people swearing by one model, but without trying others. I see a lot of opinions based on a snapshot of tooling from ~January, when for example Claude Code was exceptional, but that don't appear to have been updated. In blind tests the models appear to be much closer than some folks would have you believe.