If you think about it, it makes sense that the Separatist death count is higher than the Republic's since their army isformed by droids, ready to fight as soon as they are finished. While the clones of the Republic need training practically from birth. As for the Empire and the Rebel Alliance, the Empire inherited machinery and soldiers from the Republic and as we saw in Bad Batch they immediately began recruiting humans. On the other hand, the Rebellion as an organization took years to form, the first signs of one were in Kenobi and Andor, and as seen in Rebels, Episodes IV, V AND VI their numbers were much lower compared to those of the Empire. Sorry for the long text, I wanted to add context and logic to your question.
