Honestly aside from the voice it uses you wouldn't notice a difference. Switching costs are low, vote with your wallet.
Same, just a while longer ago.
I much prefer how OpenAI models write to Anthropic's, will probably revisit Anthropic in a generation or two. Context size is more limited, but no critical forgetfulness due to compaction so far, though I also like having plan files around both for future reference and improving chances of success at long form work.
Also tried out Kimi K3, was nice but slow (and apparently routed some requests to Claude anyways), GLM 5.3 was faster and still pretty good but the token allowances were kinda limited.
You need to use frontier models to understand where the puck is going, but also to use local ones for anything remotely sensitive.