On flat terrain maybe, but on rough running there's only so fast a dog can run and I don't think a greyhound would be faster, if anything it would be injured through not regulating it's speed. But, who can tell eh? It's all opinions.
Exactly ... terrain will play a massive part and a light little nippy thing would make a greyhound or a medium to large lurcher look silly on rough ground with large boulders tree stumps etc ... It's horses for courses .......