Month of year? Are you trying to hit the Flower Carpet in Brussels, otherwise not a key destination?
There is so much more to do in Antwerp, it's an easy decision for me. I've seen extensive tram line construction in the past; That can happen anywhere. But there's a lot of "transit" in Antwerp. We had a high budget, so we often stayed at the Hilton, with an Executive Floor. If you are in good health, you can walk in a different direction in Antwerp every day, and never see the same thing twice. (In fairness, I'm from NYC, where peer-reviewed research says residents walk farther than residents of other cities.)
No slam against Ghent, they are not comparable-size places. The historic buildngs in Antwerp are spread out over eight square miles. In Ghent they are all in the same 0.5 square mile, about 15 minute walk from the train station. I mention this because most such towns in Belgium have eventually dug up their lovely square to build levels of underground parking. It happens.
Antwerp has a lovely but very small botanical garden between the Magdenhuis and the (awful) Theater Square. Try not to miss a family sunday at the less-elaborate Rivierenhof park. Hard to get to without a taxi, but the outdoor Middelheim sculpture park (a bit of perennial and garden planting, but not "a garden" is huge, and has wonderful outdoor sculpture.
If you have time, consider Leuven too. It has a nice public park, and (much smaller) an exceptionally nice Beguinhof and church, along a canal, bus ride from downtown. Good town art museum, famous Town Hall exterior decoration.
(Note that the Antwerp airport is generally not in current use.)
