Having been myself in both, I would say that the main difference is the environment around.
As previous poster said, there are some nice new HDB flats really nice, and some old crap condos
Expect that a HDB will have more probably food courts, street market, ... around. A condo
will have his own facilities, but the "life" will be less. So if you are looking for a quiet place, condo would be a plus. If you are looking for mixing with the local active life, HDB.
I have been in a HBD in Bedok, very near the MRT. Now a condo in Braddell. Of course flat is nicer, but I would change my location inmediately. I had everything next to my flat before! Company is paying, so even that, I would prefer the local life.
I should say that I came to Singapore as a new experience, not for staying in "western-style areas" (for that, I would stay in Spain). The neighbours in my HDB were locals REALLY friendly. I barely know anyone in my condo now.
So is a matter of taste. With kids I would consider condo, without, and specially if you are paying yourself, HDB, but every person, one different world....