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>What is the modern power ranking on image formats?

I will assume this can be outside the web and consider only image format / codec that is state of the art.

>For lossless, what is typically the most efficient size wise? Decompression speed?

In terms of lossless, JPEG-XL is the one to look at. Both in terms of size and decompression speed. You will already see communities from professional photographers using this format.

>For lossy?

That depends on what sort of quality you are looking for. In some edge cases you could have JPEG XL being better at ultra low bit per pixel, like 0.1 bpp. Otherwise in 95% of cases, at 0.1 bpp to 0.5 bpp, it is HEIF / AVIF. HEIF based on VVC / H.266 Encoder likely to be the state of the art. With current reference FVC / H.267 implementation bringing another 10 - 30% improvement.

However the higher the quality you go, i.e 0.8 to 1.5 bpp, the more favourable to JPEG XL.