All my best dogs have been around 23-24 inches, and weighing around 40-45lb...These were used for everything..
Fo me bigger dogs would come next, because apart from rabbits, they can still do every quarry, even, in over 30 years working lurchers, Ive never seen a bigger dog that couldnt get down to rabbits...
but very small light crosses will be found wanting doing everything, and dont have the physical strength to do what I needed a lurcher to do. Rabbits obviously wouldnt be a problem, depending how many you were after of course, but as consistant takers of hare, fox and roe deer (pre ban