I dunno, just felt like conventional (since long ago) knowledge that MyISAM is the fastest of all SQL DBs in simplistic non-RAM scenarios. I'm not sure this is true so I ask.
The engine might be faster (I'm not sure) but SQLite has the advantage that it doesn't have to connect over a socket. Instead you load the SQLite library into your code and your application directly manipulates the database files. That's potentially a lot faster.
Before sqlite is definitely was said to be the fastest, I suspect the two are similar enough that it makes little or no difference these days and sqlite (unless the dynamic typing thing is an issue for you, and even that is going away as recent versions support at least some stricter type enforcement) safer and more “correct” than MyISAM in many ways.
