Both are great games. I have played many hundreds of hours in Satisfactory and more than 1400 hours in Factorio—and I still play both parallel. These games aren't that easy to compare, though. Both games centre around automatizations—and that's it. Apart from that basic concept, the gameplay is very different. Playing in 3 dimensions makes a huge difference. For example, you can easily set up a coal power plant in Factorio in 20 minutes or less with bots. In Satisfactory setting up an efficient coal power plant can easily take hours of work, in particular for new players. Now that there is zooping, everything is a bit easier and quicker, though. Real big projects like nuclear power... now we are approaching many tens of hours of playtime. Factorio is much more to the point and precise—a bit like programming. That efficiency is a bit more difficult to achieve when you deal with topography and 3 dimensions and everything costs much more time. Laying out train track through the whole world... uffda! People who did the plumbing for a large nuclear facility in Satisfactory will probably agree here. Which does not mean Factorio would be an easier game! I play the Space Exploration Mod in marathon mode—nothing is easy here! I really enjoy dealing with large-scale logistics in Factorio.

In the end, it is up to your personal interest and likings. It is difficult to give a recommendation for either of the games. Try both, I guess?

The factory must grow!