Convolutional PML is not better than Brenger's PML, there are papers discussed about this. Convolutional PML is developed by S. D. Gedney and Roden Allen, the major part of this work is to understand the PML as a Uniaxial absorbing media rather than split field stretched media, This understanding makes more sense when defining PML's parameters and the implementation is relatively more straight forward. However, the performance is actually the same.
Newer PMLs are actually called CFS-PML (Complex Frequency Shifted PML), Such PML absorbs evanescent waves.