When it comes to loading MO translation files, DynaMO leverages a characteristic of MO files to only look up individual strings vs. loading the whole file. Performant Translations on the other hand still loads the whole file, but keeps everything super lightweight. In the end, both are equally fast.
However, Performant Translations also supports the PHP file format for translations, which is faster than any other method and even uses less memory.
You can see some benchmarks over at https://github.com/swissspidy/wp-i18n-benchmarks.
To learn more about the various different approaches for translation loading optimizations, I recommend checking out the in-depth i18n performance analysis.
Hope that helps!
Edit: and before I forget, Performant Translations is planned for inclusion in the upcoming WordPress 6.5 release, so there’s that ??