Depends on how u feel about noise. If it doesn't bother you, get the one with the YSTech. If you really LIKE loud screaming fans, get the one with the Delta, you won't be disappointed.
Millisec.com comes out and lays it on you straight, probably too many returns. Might want to consider the Alpha pal35-t with the 21cfm sunon fan from the same source. Actual cooling is hardly affected, sonic suffering is greatly reduced...