It seems that most people have taken the stance that getting PBT keycaps is not necessary, I have to disagree. Since you have cherry mx blues, and I may be wrong, I'm guessing you might do a fair bit of typing. In my opinion, typing with PBT keycaps for long hours does enhance your experience.
As soon as I switched keyboards and started typing away, I immediately noticed the difference and took the PBT keycaps from my old keyboard to put them on my new keyboard. The best way to describe it is: ABS keycaps have a more glossy, frictionous feel, whilst PBT keycaps have a much smoother feel, which makes transitioning from key to key easier, and more comfortable.
It is also important to note, as somebody else suggested, that there can be good and bad quality PBT keycaps. The overall feel may differ with thickness as well as other factors.
So again, if sitting in front of a computer is something that takes up many hours of your day, and you value the quality of your typing experience during those hours, then I would strongly suggest that you consider getting better, PBT keycaps.