The bank fraud is more likely to be charged in my opinion. But it ends up being a lot more complicated than that. It isn't uncommon for a tax appraisal to be 20% off from a bank appraisal so simply have different values isn't always an issue.
It appears there are 3 different times that Trump set the price of his properties for transactions.
He argued they were lower in order to reduce property taxes.
He argued they were higher to take out loans
He also argued the value was higher when he donated the property as a tax write off.
One of the questions is going to be who did the appraisals, were the appraisers corrupted in some fashion, and how and when were the different appraisals used for Trump's advantage.