The Logitech G903 is marginally better than the Logitech G403 Wireless Gaming Mouse. While both have tremendous gaming capabilities, the G903 has a few more buttons, you can unlock its scroll wheel for infinite scrolling and it features tilt inputs as well. Performance-wise, they are very similar, although the click latency of the G903 is a bit lower and therefore can feel a bit more responsive. On the other hand, if you prefer ergo-shaped mice, the G403 wireless might be a better option than the ambidextrous design of the G903.