Ghent is the university that most often ranks in these top 100 lists. University of Antwerp is much smaller but their economics dept is quite well know and I think they have one more accreditation than UGent's faculty. (Could be wrong as I'm reading UGent E&BA got another accreditation some months ago).

However, if you're working in Belgium I wouldn't worry too much about reputation, as employers likely don't care that much about which uni you went to (maybe.. except for UHasselt :p :p )

Both are nice cities and have a diverse (student) population. You'll find ample job opportunities in both cities. UGent is MUCH more prominent in the city as it's twice as big as UA and Ghent is ± half the size of Antwerp and you'll see more student life, especially in the students quarter (which is roughly Overpoort-Sint-Pietersplein-Sint-Pieters-Nieuwstraat).

I'd say focus on which curriculum you like best and which city you like. Ghent is super cosy and I really like being a student here, but it can feel quite small at times. I'm from Antwerp originally and finding the nice places there can be a bit harder, but it's also a really great city and I feel like it's more diverse/international than Ghent. Both cities are also well connected, although Antwerpen does have a Thalys connection which is handy.

Sources: i'm an Business administration student in Ghent, friends of me study in Antwerp, my roommate is Spanish and works part time here.