Well for almost sure PBT434 has a better safety profile than DFP. Both can remove the labile(free) iron, which is thought to be the problem, but DFP removes it with a much stronger binding force, capable of removing iron from cell stores, and that can create problems.
DFP Kb=10-36 PBT434 Kb=10-10
DFP even has a stronger zinc attraction than PBT2.
For anyone interested have a look at page 14 of this Dr Stamler presentation to see the effect of DFP iron chelation on patients in a 6 month study.