I wouldn't trust either one. Get the image onto a calibrated TV and use that for this type of quality control.
I don't think you understand, both windows are right next to each other on the same calibrated monitor. I never had this problem before CC, so it must be a bug.
Try updating or rolling back your video driver.
What is your Premiere Monitor Playback Res set at?
What is the Preview Setting?
Jims advice is useless in this instance. He expects you to do an output file everytime you make a tweak in Titler or Sequence just to see what you might abitrarily be getting.