In regions with slow internet (2-10 Mbps), downloading a 4GB ISO takes 5+ hours. A compressed 500MB file takes 30 minutes.
Ideal for users with capped internet or slow speeds. Ps2 Iso Highly Compressed
On mobile devices, you can use format. CHD is superior to CSO—it offers higher compression ratios without performance loss. In regions with slow internet (2-10 Mbps), downloading
Different formats offer a trade-off between file size and compatibility with emulators or real hardware. [FR] Support for cso/gzip/chd compressed ISOs #225 - GitHub 30-Sept-2019 — or even original hardware
For modern emulation on PC, Android, or even original hardware, the best approach is to use Lossless Compression