I suspect I'll get some flak for saying, but I don't think of the Invitational as a true reflection of the best dogs competing. Instead it is a show case side-show to the conformation event. For many of the not so popular agility breeds the 5 "top" dogs invited may possibly be the best 5 in that breed. But for any popular agility breed (read as highly competitive), such as bc's and shelties & a number of others, then the rules by which invitations are determined strongly favor those with very deep pockets and an availability of time to be competing all the time in order to garner the points.
It is a nice show to see the diversity & good for those to have their day, but the standard of competition is far higher at our local trials than it is at the Invitational.