My experience suggests to me that hotel properties within the DoubleTree brand can be wildly inconsistent; while hotel properties within the Hilton Garden Inn brand are so consistent that an experience at one of them is quite predictable. I know what to expect at a Hilton Garden Inn; and the experience is usually good for me.
One exception is a Hilton Garden Inn at which I stayed in Lancaster, Pennsylvania — which I believe is one of the four original Hilton Garden Inn hotel properties.