Generally speaking, there should be little difference between an analog signal and a digital signal. An analog signal is basically a converted digital signal, so there is always a possibility of some signal degradation.
There is a difference between watching a movie on an IPS panel vs. a TN panel. TN panels use dithering technology to generate 16.7m colors from only 256k actual colors. This can create artifacts on the screen; either color banding issues with color gradients or general pixellation that are not actually in the source material.
Inexpensive IPS monitors use the e-IPS which almost all use 6-bit color technology just like all TN panels monitors. There is only one or two 8-bit e-IPS panels manufactured and only a very few...