Even if they're both USB 2.0 and plugged into USB 2.0 sockets, there can still be a large difference in speeds, especially write speed.
It has to do with the particular type of flash memory each drive uses. Some types are much faster than others.
Unfortunately, I have not yet found a reliable way of looking up what types of flash each manufacturer is using. Some manufacturers even use different types in different products within their own line.
One of my fastest flash drives is a 1GB from a no-name manufacturer (found it in a bin at Fry's for $19.99). I also have a 512MB SanDisk Cruzer (name brand drive), it's slower than molasses.
Thus, it's a toss up, your guess is as good as mine, your mileage may vary, do not hold in hand, objects in mirror are closer than they appear, do not taunt Happy Fun Ball, etc. :roll: 8)