He was a serious historian who tried to be balanced
He had 2 major drawbacks: 1) He tended to side with the Lancastrians against the Yorkists and blame the Yorkists for starting the Wars of the Roses, 2) He was writing 50 years after the events he described so he could not talk to any survivors and had to rely entirely on written sources
They are extremely useful because: 1) The authors had no reason to write anything other than what they believed to be true, 2) The authors were usually in London so they would be informed about what was happening there, 3) They were written at the time of the events they were describing, 4) The Pastons were not directly involved in the Wars of the Roses and were not committed to either side
As Abbot of St Albans he was involved in national politics, he had something of a Yorkist bias but was independent and not afraid to criticise either side when he thought it was justified
A Burgundian chronicler, any Burgundian chronicle would show a Yorkist bias because the Yorkists favoured alliance with Burgundy while the Lancastrians were pro-French
Lived in Rome and relied on hearsay or second-hand reports about England, nevertheless the fact that Pius II had heard how mentally feeble Henry VI was shows how well known this was
John Hardyng was a northerner by birth but worked for both Henry VI and York at different times, so his bias would depend on who was employing him at the time