Beside the different silicon cell design, the most important difference between NAND and NOR Flash is the bus interface. NOR Flash is connected to a address / data bus direct like other memory devices as SRAM etc. NAND Flash uses a multiplexed I/O Interface with some additional control pins. NAND flash is a sequential access device appropriate for mass storage applications, while NOR flash is a random access device appropriate for code storage application.NOR Flash can be used for code storage and code execution. Code stored on NAND Flash can't be executed frome there. It must be loaded into RAM memory and executed from there.
NOR NAND
Interface Bus I/O
Cell Size Large Small
Cell Cost High Low
Read Time Fast Slow
Program Time single Byte Fast Slow
Program Time multi Byte Slow Fast
Erase Time Slow Fast
Power consumption High Low, but requires additional RAM
Can execute code Yes No, but newer chips can execute a small loader out of the first page
Bit twiddling nearly unrestricted 1-3 times, also known as "partial page program restriction"
Bad blocks at ship time No Allowed
Some facts about write speed.
NAND is typically faster than NOR for large writes. A typical NOR write is 10uS per word, which results in 1280uS per 512 bytes on a 32-bit bus. A typical NAND write is 50nS per byte + 10uS page seek + 200uS program which results in 236uS per 512 bytes on a 8 bit bus.
As NAND Flash is cheaper than NOR Flash and has a very slim interface it was selected as the optimum solution for large nonvolatile storage applications such as solid state file storage, digital audio/voice recorder, digital still camera and portable applications requiring non-volatility.
以上內容轉自：http://blog.csdn.net/hxliu_leo/archive/2010/03/09/5360097.aspx
在嵌入式系統中有 jffs和yaffs文件系統，jffs文件系統一般掛在nor flash上，而yaffs文件系統則針對nand flash做了專門的優化，所以一般掛在nand flash上。