TLDR: FT for playability, Pred for eye candy.
I think on the FT side the classes better difference themselves because different styles of play are still effective. The only really unique playable Pred DLC has been Valkryie imo because she really is a perfect build for hit and run style. Scout too squishy for it and Hunter just a bit too slow to be effective but Valkryie nails it perfect without being OP.
Elder has only really become a huge standout with Specializations, and Alpha just feels like a slightly thicker scout. City Hunter tweaks are so minor from Hunter now, and your forced to carry the wrist launcher that has no positive affect on play style. Viking and Samurai are just a Zerkers with minor tweaks. Visually I think they’re all phenomenal but they play the same way as the three default classes.
Where as the Dutches, Dante, OWLF and now Isabelle definitely have a whole different feel and playstyle too them. That’s even without taking Specializations into consideration, they just have a different feel and style to them and are more unique than their pred counterparts.