A 50Hz set would be designed for PAL, so DVDs transferred at 25fps and mastered for PAL should look smooth, but playing NTSC DVDs, which are converted from 24fps to 30fps at 60Hz and then played back through a 50hz monitor would likely display jerkiness due to the various speed changes, which might have been masked on a CRT's slower response time.
I run movies (NTSC, PAL, and Blu-ray 24p) through an LCD projector (Panasonic AE 2000) and find that many if not most DVDs look drastically better than on an old CRT whereas certain others actually look much, much
worse than they do on an old CRT. It's likely a combination of your TV set's capabilites, the configurations (through the setup menu) of both your TV and Blu-ray/DVD player, and also how any particular DVD or Blu-ray was mastered, authored, and compressed.
I've found that a more than a few 24p Blu-ray transfers still seem to have inexplicable skips in picture action on occasion. I expect this may be due to either faulty mastering, or a disc error that results in the player continuing to display one frame for two or three frame-cycles until it gets good data again. There may be similar things happening on DVD playbacks that look jerky (it happens all the time on digital TV broadcasts with both picture and sound together or one or the other separately). While analog video may have its own problems, it tends to deal with video and audio signal anomalies in a much smoother, less distracting way than digital video does. Someone else may have more detailed (or accurate) information about such playback problems).
--Christopher Jacobs
http://www.und.edu/instruct/cjacobs
http://www.und.edu/instruct/cjacobs/Old ... BluRay.htm
http://hpr1.com/film