The diffrence is subtle.
However the change in bit rate provides a higher maximum frequency which is half the sample rate. 44.1 = maximum frequency of 22.05KHz. 48 = 24KHz. and 96 = 48KHz. All of which are above the range of human hearing.
This is the case to avoid digital quantization noise at the A/D Convertor.
the 48KHz is used for film as it relates to the NTSC format.
Bit depth on the other hand (16 or 24 bit) gives the number of digital quntization steps. This means 24bit sounds better because the sounds are more accurate to the origional sound.
Dither is applied to a master ONLY when the bit depth is reduce from 24 to 16 bit in order to mask any quantization errors.
Hope that helps
G