It depends on other factors too, type of land you hunt, your main quarry, method of hunting etc.
As for me, at the minute I have a lurcher/lurcher bred dog, I have owned for 5 years, a good friend of mine has bred the same type for 20 odd years, the dog has a lot of whippet in his make up and stands at just under 24 inch, he has takes rabbits with ease, has caught a few hares in his time (although obviously not great numbers!), regularly takes fox and even pulled 2 roe (one with assistance ) He has never let me down in the five years I have owned him. I have had bigger dogs in my time, so