It's not really as simple as "it's a good area" or "it's a bad area". You need to take a look at both houses, see what they are like, and most importantly, where they are located in the estate.
In general, Clonee has a pretty high number of rental properties although I think this number is beginning to fall. Rental properties can bring their own issues to an area as everyone knows. There's a lot of houses in the area (thousands) and this might put some people off. Personally I think you can be lucky and get a well positioned house, not much overlooked and in a quiet cul-de-sac, or you could get a house close to the entrance to a large estate, have parking and traffic problems, be overlooked and have kids hanging around the place.
You need to decide what would bother you and what would not. Lots of people would say Castleknock is a nicer place to live in D15, but again it all depends on where. I've seen houses off Auburn Ave that are cramped, tiny, little parking space and kids hanging about the place for €100k more than a better house in Clonee. Personally I don't see there as being any different to much of Clonee, but some people might.
Beechfield does have those duplex apartments which I'd not be wild about either, so check the situation with them as regards parking and so on.