What do Jessica and Lorenzo think of Portia? Why is their opinion important enough for Shakespeare to show?

They show adoration to Portia:

Past all expressing. It is very meet

The Lord Bassanio live an upright life,

For having such a blessing in his lady,

He finds the joys of heaven here on earth.

Explanation:

This is important for Shakespeare to show, because Portia is the one who will deal with all the problems and satisfy the Christians in the play. She is a person who enables Jessica's conversion to Christianity and her marriage to Lancelot.