Performance comparison between internal and external memory What are the performance differences between phone's internal memory, the internal SD card, and the external SD card? I wonder if that counts when deciding where to store apps. What technologies are used for building a phone's internal memory? How about the internal SD card, if it is not really an SD card at all? How do they compare, in general, to SD card speed classes 4, 6 and 10?

Note that I am not asking about the filesystems, as a deleted answer focused on, since performance comparison on this aspect would be totally ruined by just switching the SD card from FAT32 to something better (which I think the industry should have done since a long time anyway).
For what's worth, I had a class 4 SD card. Running games whose data was on that external SD was painfully slow, during loading and during gameplay, with frequent mini-freezes. After upgrading to a class 10 card, I find no difference in running games from the internal and the external storage.

Please don't draw any conclusions from these highly rigorous scientific experiments.