Visiting a place for a first time is like having a blank canvas. If you are travelling alone is quite possible that, no one knows you, no one. And you have a whole place like you have never seen before so explore.
When you return to a place, certainly after many years when you have had an experience of the place. Hopefully if you made my mistakes you will have learned from them.
That is unless you had to return to a place against your will. But really you would not have to do this unless your trip ran into some visa issues, or in the event of an emergency.
It's always good to see a new place, but often there is a place that is calling you back. Or there is a place that you are longing to return to. If that is the case, you certainly won't quit thinking about that place until you have returned. In that case you should return.
But you are having a second experience it can be just as exciting. It doesn't have to be more of the same. For it to be different, you will have to do something totally different. If you spent some time there, and acquired some good knowledge of the place, it is entirely possible for it be a rewarding return visit.
Perhaps there is something that you did last last time, or even something that you wished you hadn't. There is always something that we wished we saw more of. Looking back at your travel photos, you'll find some inspiration.
As the old Apple slogan once said, think different.