Most PR systems weaken the link between MPs and their constituents. Actually, it is not very strong with FPTP and STV would strengthen it.
Most PR systems would strengthen party power and reduce voter power compared with FPTP. STV would reduce party power and strengthen voter power.
Most PR systems encourage factions within parties to split off and form their own parties, which can lead to a large number of small parties and instability, as especially in Israel. STV helps factions within parties (e.g. pro or anti EU or pro or anti a local bypass) to express their views within the party without leaving it.
With most PR systems and, indeed with FPTP, post-election coalitions are formed by politicians behind closed doors. With STV, voters can tell the politicians which coalition they would prefer and punish them at the following election if the politicians ignore them. For example, Conservative voters could show with their later preferences whether they preferred coalition with UKIP or the Lib Dems. Lib Dems could indicate whether they preferred coalition with Labour or Conservative.
Although all PR systems provide fairer representation of parties than FPTP does, only STV also provides fairer representation of people.