The Google Play process is more thorough. There are a lot of steps and you need to clear them one by one. This means waiting several days between each step. The Play Console dashboard is quite well documented to be honest but can be overwhelming. The main obstacle is that you need to find at least 12 testers to play your game for 2 weeks straight. I ended up paying a service to test my app.
On iOS, the process is a bit more obscure. It's fairly easy to submit an app, but then you don't really know what's happening. You can only see a status like "Pending review". And then one day, you are approved.
Overall, the iOS process felt easier for me. As long as your build succeeds and you provide the correct information, your game can be live within a week. The Android process took more than a month in total.