The chipset is exactly the same, or else you couldn't cross-flash (but you can). The chipsets for all liteons since the 16102B are from MediaTEK. What's different (according to Liteon) is the PUH used. According to Liteon S stands for Sanyo PUH; I have no idea what W stands for.
While I know that some people have flashed their drives from S to W, I wouldn't recommend that - unless you absolutely need a certain feature.