Rather than a new method, the only change affecting translators is that xliff files have substituted .po ones for offline translation, and that only for Transifex translation project. (Not for the plethora of projects hosted in https://www.transifex.com ). Again, this only affect those of us who use offline translation tools.
I was firstly concerned with the change, because of the lack of free .xliff editors and of loosing the ability to use any translation memory creating through working with .po files. Poedit seems to provide a nice solution: with it you open .xlf files as you’d do with .po ones. No need for any extra steep. After opening it, you forget about it being a .xlf file: all Poedit capabilities are available.
P.S. I don’t know which format is better and in what cases