Question Best Way to Get from Istanbul to Kusadasi Without Flying?

We’re spending a few days in Istanbul this May then need to get to Kusadasi. We don’t want to fly, so I’m looking for the best transportation options. I’ve heard about buses and trains, but I’m not sure which is more reliable or comfortable. Has anyone made this trip before? How long does it usually take, and are there any tips for making the journey smoother? Also, if there are any scenic routes or stops worth checking out along the way, I’d love to hear about them!