MS2 wrote:If we go with a historical-type interpretation, Jesus was predicting that the oppressed among the Jews would soon have their situation dramatically improved when Yahweh acted to throw out the Romans and bring in his own kingdom (ie the kingdom of God). This is reflected in Luke's version: 'Blessed are you who are poor, for yours is [ie will be] the kingdom of God.' Matthew though, when writing his version, realised that the poor were still suffering and that the kingdom had not actually come, at least in a physical sense, eg with the overthrow of the Romans. So Matthew 'saves the day' by spiritualising the saying: and it becomes the spiritually poor who will be blessed, and the kingdom itself is 'of heaven', rather than one that will come about 'on earth'.
I think Luke's version is just down to bad reporting - the person who was there didn't understand the 'in spirit' bit or didn't hear it properly so it was just left as 'Blessed are the poor...' hence the NEB version I quoted above.