@srol most SD cards are designed for very few writes and lots and lots of reads, because they're typically used for cameras and stuff like that
sometimes write-heavy usage can cause corruption; for example a while back I ran a pleroma (times were different back then) on an SD card and pleroma writes a *ton* to the database, just all the time, constantly
anyway this caused some pretty bad crashes
there are higher-quality "application class" SD cards which aren't as bad as the normal type, but the EMMC will be more reliable in the long run