On the one hand, I understand the point of view that the PL must have more evidence than the few emails that were available at CAS. For example, they have presumably had access to all relevant email records and all relevant accounting records which may well have raised considerably more questions. I think it's undeniable they will have more information on which to build their case.
On the other hand, I ask myself exactly what sufficiently cogent evidence they could possibly have that proves on the balance of probabilities that, for example, Mansour provided money to Etihad to pay their sponsorship. There is nothing in the club's accounting or other records that could prove that to the required standard, all the evidence they would need is at third parties. And there has been no indication at all of a third-party whistle-blower or incriminating supporting evidence from third parties.
So, as at CAS, it's most likely a question of balancing circumstantial evidence (things said in emails, things said in presentations, etc) against witness testimony and accounting evidence from the third parties.
I was struggling to see how the PL can clear that hurdle 18 months ago, and I am still struggling.