We replaced our mish-mash of original hardwood single glazed and cheap softwood double glazed with upvc double and triple glazed last winter. Our garden backs onto a dual carriageway with a mound separating us from it.
In the sitting room, where the windows fitted very well and there was ventilation via the chimney, it has not made much difference, if any. There may be less draught from the windows, but you can't tell with the curtains.
In the bedrooms where the vetilation was not good, the frames were rotting (slowly because was hardwood, but the putty had been in a bad way for years). I had to wipe them each morning and open them slightly to dry in the sun, and they still had black mould. These are much better. With the triple glazing, there is still a tinny hum from the road, if you listen for it. It is less disturbing, and the noise from the flats to the side (shouting, car doors, motorbikes) is greatly reduced. There is fine condensation on a very cold morning.
The large wooden double glazed custom made window, that was left, is noisiest. I suspect it is because the windows do not close tightly enough and the insulation is not good enough. Also, the gap in between the panes of glass in the sealed units is narrower than the new windows.
On the downside, the upvc ones expand in the summer sun and make the windows difficult to close again, until the evening. This was never a problem with the hardwood.
Ideally, I would have had double glazed hardwood, but that would have been double the cost of upvc and we have a lot of windows, mainly at the back of the house. Since everyone else in the area has used upvc, and some have even used white, there was no point paying so much more for them.