Complex sentence: One difficulty with some of these modes is that the grating on PAL and NTSC televisions is very different, as is the update speed, so often the modes that display well on European systems display awfully on US systems, or vice versa.
Split into simpler sentences: One difficulty with some of these modes is that the grating on PAL and NTSC televisions is very different, as is the refresh rate. Often, modes that display well on European systems display awfully on US systems, or vice versa.