5 day in Belgium, Ghent or Antwerp as base?

You can further reduce your hotel changes by having Gent as a base. Half an hour by very frequent trains from both Brugge and Brussel, and one hour from Antwerpen. Gent is an interesting and lively city.

I did five nights in Belgium last May, so I had more time than you. I had a list of small villages and didn't have time to make it to a single one. I spent 3 nights in Ghent and 2 nights in Antwerp and did day trips to Bruges and Brussels.

I agree with tonfromleiden that Ghent might be a better choice as your base. I'm not sure why your priority is to stay in Bruges one night. Since it's just a half hour from Ghent, if you stay in Ghent, you can spend a long day in Bruges, including staying later into the evening. Another reason to stay in Ghent is that the city is beautifully lit up at night. I'd recommend staying all four nights in Ghent.

It's been noted here that students keep prices down a bit in Gent. I prefer Antwerp because there is so much to do. You might consider where you can get an affordable hotel within a short walk of the train station. You are quite right to plan multiple day trips, since Belgium is perfect for that. I would never spend the night in Bruges.

Myself, I would stay in Ghent all 4 nights and day trip to the others. But, if your priority is to spend a night in Bruges and you don't want to do a lot of hotel changing, then why don't you just make your base there for the 4 nights and day trip to Ghent, Antwerp, and Brussels. A lot of people here love staying in Bruges and it's just as easy to get from there to the others as the other way around. That way you get to see a lot of Bruges without the crowds, utilizing the early mornings and evenings there.

Reason I opt for Antwerp is because I am assuming there is much more to see and do in Antwerp compared to Ghent.

Additionally Brugge is the place that I wanted to visit in Belgium as priority hence the reason for an overnight stay. I presume Brugge is also beautifully illuminated at night.