Here is a comparison between Gemini 3.8 Flash and Gemini 4 Hydrogen (the new Flash model). The results are not even close.
Additionally, Hydrogen will launch with a new 4th thinking effort: `xhigh`.
1st video: Gemini 4 Hydrogen
2nd video: Gemini 3.8 Flash
From what I've tested and seen, Gemini 4 Hydrogen seems to be a distill of Gemini 4 Carbon specifically.
It's a fast model, inherits Carbon's mannerisms (which are much better than Argon's imo) and rivals Argon at a much lower cost.
It will be a good Flash model definitely.