I prefer Maastricht. It's a host for three countries incl. Belgium and Germany. It is perfectly centered, many fans won't need airplanes. Not even me from Austria, it would be a 7h car ride. And if you need airplanes, international airports are close enough.
Never been to Maastricht, but it looks beautiful and I endorse the European spirit.
So, I have been to Rotterdam 6 years ago and I am not sure why fans are so excited about that city. It is very flat and windy and architecture is bleak. It's a concrete desert. The airport is also really small, so you can also just book your flights, if you need one to Brussels or Amsterdam and book a train ticket.
Amsterdam truly is a wonderful city but I totally get why they are not keen on more tourists. It already is overrun. And unlike Vienna, the city is not greedy for more.
I think Vienna also did not need Eurovision, because it is overrun. But then, Vienna propelled itself to the number 1 destination for LGBT in 2015, so I guess they were keen on that "reward". Graz or Linz would have been my choices, because they are lesser known and have bigger arenas, but probably not exciting places for LGBT.
But well, it is always interesting to have Eurovision not in the actual capital.