First x bulls are decent because there not as heavy as the line bred halfxs so I find the first x a tad faster then when you start doing 3rd 4th generation half x etc.. Seen a few first x saluki out of that Khan jihad but wasn't worth a wank tbh and I had a first x Beddy bitch break a ditch in two halfs for a rabbit on the lamp just lacked the size for continuous fox work, but I run mainly fox so it's a bull x or Wheaton x for me but obviously depends on what your running.