During my summer vacation in Brussels I visited several Beguinages.
The most beautiful for me was the one Leuven. It is large, full of red brick buildings, has several bridges over canals and lots of green. Together with the lovely town hall this was the peak of this truly charming city!
Bruges is also impressive. I loved the location close to the canals and the Minnewater as well as the large court with trees. The white paint of the houses and the unimpressive church spoiled the impression for me a little.
In Gent I visited all three Beguinages and was a bit confused: While it is clear that the Klein Begijnhof and St.Amandsberg have Unesco status there is some confusion about the Oude Begijnhof. In the (otherwise excellent) tourist information in the vismarkt I was told that all three are Unesco sites and there are official signs to it with the Unesco sign! Anyway, I walked there since it is close to the center. It is a nice place though there are no outer walls anymore and it is not well signed. I couldn't finde a map that would show which of the surrounding blocks were part of the beguinages.
To the south east from the center is the Klein Begijnhof, with is very nice though at the time they are doing some renovation work, but that is eventually a good thing. It isn't really that small and has several streets from different periods and an impressive church (I could only see the outside).
The most impressive of the three was certainly St.Amandsberg (15 minutes by bus 6 from "Zuid", close to the Klein Begijnhof). About as big as Leuven, with a big gothic church and build entirely of a dark red brick. It has three squares and about eight streets. It is very unified in style since it was build on the site of an old beguinage in 1874. Obviously there were still many beguinages at that time!
If you are in Brussels visit also the tiny Beguinage in Anderlechen (a part of Brussels). It has a nice little museum with an excellent film about the Beguines. Included in the ticket for 1.25 Euros (!!!) is the visit to the Erasmus house with a charming garden.