It’s hard to compare people in different eras. Erdos certainly wrote down a vast number of notes that didn’t become published. I think much of Euler’s volumes that are mentioned in the link you supplied would be considered notes nowadays. Erdos also worked in an era where collaboration became essential. In Euler’s era that wasn’t as essential as it is today. Euler also worked in an era where there was a lot of low hanging fruit so to speak. None of this diminishes Euler’s accomplishments and he is certainly regarded as a greater mathematician than Erdos.