Thank you @Ezra Morley! The comparison website is very helpful. So when you’re comparing cameras from the same year (or close to it) pixel size matters, but not as much when you’re comparing old and new cameras.
I’ve notices that full frame cameras almost always have larger pixel size. Why don’t manufactures keep a large pixel size for crop sensor cameras and just make less megapixels? Are they just trying to make crop sensors look better then they really are?