got my g203 and it replaced the g pro, mainly because of the less stiff cable. other than that, the mice are pretty much identical in shape and weight. the buttons on the g pro are better tensioned though, i can click faster with them than with those on the g203.the 3366 sensor was perfect for me, and so is mercury. i couldn't feel a difference, both are snappy and keep tracking at whatever speed. that's however just the plain in-game experience.