Knocklyon Park and Knocklyon Close are both lovely estates, not sure of the ages, would think they are both around the same age.
The whole area is quiet, settled, mature, amenities close by, shops, doctors, dentists, takeaways, schools, M50, etc... It has everything.
A nicer area for sure than Prospect Manor - as in well settled, plus the advantage that no major changes are going to happen within a mile of you, its all already built and in place - you wont get a sudden shock at a new facility that you dont like being built on your doorstep.
If you can afford it, my opinion is that Knocklyon is the better area - hoping to get back there myself some day.
If its a choice between those two estates in particular Id say check out the ages of both and the house size as there is nothing external to be a contributing factor.