Quote - BUT is Poser PRO worth the $250 for an upgrade? Will I experience higher quality renders?
Will complex animations be easier?
Will all my Poser Characters work with it?

All of your character should work fine, I haven't come across any problems. I can't comment on any of the newest generation DAZ characters (M4 & V4) since I don't use them.

 

I have Poser Pro and V4 and M4 work just fine for me.  Plus Poser Pro seems to be very
stable.  I can't recall the last time it crashed, if ever. 

I also like that I can use the queue manager to  render an animation with another old computer
I have and not tie up my main machine.