I have both the G303 and the G302 and the G302 feels far worse.
The G302 cord is MUCH MUCH stiffer. This was my main complaint with the G302 overall, the cord was just so much stiffer than any cord I had ever used and it messed me up quite often. The G302 sensor also feels noticeably worse than the G303 sensor (in my opinion, not a big difference though obviously) and the G302 doesn't have mouse feet on the sides of the mouse, only on the front and the back, so it feels almost wobbly as you slide it across your mouse pad
I enjoy my G303 far far more than my G302 based on these few changes. You said the G302 is 10 dollars cheaper but I would say the 10 dollar difference is worth it based on the differences between the two