In theory, yes. Raw mmc read speed is 1,5MB/s, raw internal flash read speed is 4MB/s (both measured by dd utility). In reality it is hard to notice. Internal flash uses jffs2 filesystem which is compressed. This saves space in flash but takes cpu cycles to decompress and slows things down both for reading and writing. It even feels to me that ext2 on mmc is a bit faster than jffs2 on internal flash. I may get some numbers in future but I know I can hardly tell whether I booted from mmc or internal flash without using df utility to check :-)