There is no doubt that both the Avago 3988 and Pixart 3366 are great sensors. However, there are a few things that you should consider before deciding which one is better for you.
The main difference between the two sensors is that the Avago 3988 is an optical sensor while the Pixart 3366 is a laser sensor. This means that the Avago 3988 is more suited for use with a mousepad while the Pixart 3366 is more suited for use with a hard surface.
Another difference is that the Avago 3988 has a higher maximum DPI of 12,000 while the Pixart 3366 has a maximum DPI of 8,200. This means that the Avago 3988 is better for people who like to have a higher DPI for their gaming or for use with a large screen.
Finally, the Avago 3988 is a little bit more expensive than the Pixart 3366. However, this is to be expected since it is a more premium sensor.
So, which sensor is better? That really depends on your needs. If you need a high DPI sensor for gaming or for use with a large screen, then the Avago 3988 is the better choice. However, if you just need a good sensor for use with a mousepad, then the Pixart 3366 is a great choice.