SUMMARY
The idea that larger camera pixels are always better for image quality, especially in low light, is mostly incorrect. While individual small pixels on high-resolution sensors gather less light and appear noisier, downsampling an image from a high-megapixel sensor to match a lower-megapixel one effectively averages out this noise. The total light gathered by a sensor is determined by its area, not how it's divided into pixels. A genuine advantage for larger pixels can exist in extreme low-light conditions where read noise dominates, and also in video due to different readout processes.
TAKEAWAYS
Larger pixels do not automatically guarantee cleaner images; downsampling high-resolution images mitigates per-pixel noise.
Total light gathered by a sensor depends on its area, not the size of individual pixels.
A true advantage for larger pixels exists in deep shadows at high ISO and in certain video applications.
Pixel pitch is the wrong metric to focus on when comparing overall sensor performance differences.