Good question , mate !
They were/are around the same height and weight, the older bitch was 29” and 75lb, the new bitch has levelled out at just over 28” and 71lb.
The older bitch matured much more quickly, killing daytime hare regularly at one year old, the new bitch was slower to mature.
Id say the new bitch is slightly faster, strangely, as she’s out of a coursing bred greyhound, and a fraction sharper on the turn, but the older bitch seemed to have more stamina. Possibly the opposite to what their breeding would suggest.
BUT; they both are/were a joy to watch in full fl