Range: Digital Vs Analogue
With analogue radio systems, as the signal gets weaker noise becomes stronger until eventually the signal is lost in the noise and becomes un-intelligible.
Digital systems give as much as 25% better perceived range than their analogue equivalents (this is a figure based on perception rather than any measurable parameter,) but experienced radio users can understand speech in the weakest noisiest analogue signals so to them range is very similar between analogue and digital. With a digital radio system there is no noise even with weak signals, even as range approaches its maximum. Therefore intelligibility is perfect right up until the signal disappears.
Of course there is a down-side to this: Moving only a metre or so may take you outside of the range limits of your digital radio system, you will have had no prior warning that you were in a weak signal coverage area (there was no increasing noise to warn you). Suddenly you are out of range and you are not even aware of it.
Because analogue systems get noisier as you approach limits of range you get a warning to move back into range. Users of analogue radio systems know that increasing noise means weaker signals and if the can they take appropriate action to get back into coverage area.
Considering these facts it can be seen that digital systems will be the best solution where boundaries to the working area are clearly defined and 100% radio coverage can be arranged. Factories, enclosed sites and buildings being good examples.
Analogue lends itself to sites or rural areas where 100% coverage cannot be achieved but where users have the opportunity to move to a better location when making calls, Estate, Marine and Search and Rescue radio systems being good examples.