The first question I have with this text is why do we need another comparison with yet another Old Testament character? Already our writer has compared Jesus with the Old Testament prophets and angels. Already we've had quotation after quotation from the Psalms and from Isaiah. You start to think, "Enough already!" Do we really need another comparison of Jesus with Moses?
The reason, I think, becomes obvious when we remember the first audience - the first listeners - to this letter. It's called the "Letter to the Hebrews" because it is directed primarily to Jewish believers who face heated opposition from Jews who felt any conversion to Jesus, the Messiah, was a blasphemous betrayal of the Judaic religion. And so these Jewish believers were in danger of being pressured to turn back from Christ to the law.