I think HDBs can vary a lot. Most of the earlier ones I experienced (older owners) were older and dated themselves. Things like bathroom off the kitchen. The soil-pipe from the unit above being surface mounted down the bathroom wall. Surface mounted plumbing. And because people walking along the external corridor would look in, then there was a sheet of obscured perspex across the open windows to stop that. In one such example the citizens of the area had voted for 'the wrong party' so the exteriors of the buildings were getting shabby too. So those 2-3 cases were what informed my view. Pretty run-down, cramped, underlit.
Then a couple of years back I went to lunch with some friends of my wife and the difference was amazing. They had a new HDB and the first thing that struck was the size, it was huge, bigger than any flat I've ever lived in... *huge*, maybe 2000ft-2500ft?
I also know someone in an HDB near a sports complex, which for me would add the typical 'condo facilities' HDBs can lack. So when we were flat-hunting last time I know we tried to tie together the new HDB element, together with the local facilities. So it's not as if I ruled out renting an HDB, it just didn't come together that way that time.
Something else that might come into play; where do these newer HDBs get built? It seems to be on the periphery (Punggol etc). But IME expats usually have a desire to live closer into town, unless they've triangulated on the likes of Woodlands for proximity to the American School. Perhaps it's how native you want to go (predicting which can be hard, esp for a new arrival). I've described before wondering in the big mall by Yishun MRT and a local child of maybe 2.5-3 stopping dead in her tracks, pointing at me, and bursting into tears
It was amusing but also alienating, and Yishun is what I mentally consider a pretty 'Zone 2-3 [of 5] kind of neighbourhood.
So I think age of an HDB can matter a lot, since it's perhaps very limited the extent to which surface plumbing etc be 'modernised'/made a bit more discreet, whilst it is occupied. And age of HDBs is not something you often see described in listings IME.