Gates aren't types of memory, they're building blocks for logic circuits. Memory happens to use them.
NAND/
NOR gates are quite simple by themselves, but using them in large blocks can get complex. Usually people try to use only one type of gate because it simplifies routing & placement of signals in a logic circuit.
To answer your question, tape drives are sequential like the NAND memory architecture. But they are many times faster since they don't have moving mechanical parts like tapes, so for small array sizes, they are effectively random access. Also, something else to keep in mind is that deleting a file on a filesystem merely involves removing the file's entry from the filesystem table.. nothing more. And presumably the filesystem table is stored at or near the start of the memory in a flash memory chip. And there are many ways to 'cache' changes so they appear instantaneous to a user but actually happen over a slightly longer period of time than they appear to be. The wonders of modern computers.
