WebP has both lossless and lossy compression support, they aren't inherently any different from .png image quality unless you specifically choose to make them so. On average the lossless WebP is 25% smaller than a PNG, while the lossy version size depends entirely on what image quality you choose - set it to 0 and you get tiny, absolutely horrendeous images, set it to 100 and they look almost as good as PNG, but are basically JPG in size.
For example, taking the Hex banner image, the png is 2.4MB, lossless WebP is 1.5MB, 100% quality lossy is 0.6MB, 80% is 0.2MB, and the 0% is only 34KB but looks as attached :P
Viewing post in Web version changes coming soon. comments
In this case, I had a predefined target I wanted the total assets to reach, so I went with a level of quality that got me there. It’s all budgeting though, if the game does really well I’ll be able to offer larger files. I think the game ran well enough on the web with the PNGs so I could likely go all the way up to 100% quality if I can budget the for the bandwidth.
Makes sense, that's a quick and easy solution.
One thing you could still play with is using different levels for different types of assets - especially compressing backgrounds with lots of details and noise with lossy WebP will provide a *massive* size improvements compared to PNG which is terrible at compressing that (as showcased in my example of 2.4 -> 0.6/0.2), which could allow you to still use lossless for the sprites. Kinda best of both worlds.
But mostly, I just wanted to make sure you knew that lossless is an option for you to use :)