"Street Cred equals the character’s total Karma, divided by 10, always rounded down [...] At the gamemaster’s discretion, additional Street Cred points can be awarded [...] Street Cred is applied as a positive Limit Modifier to all Social Tests in situations where the character’s reputation would be known."
No difference between the two origins for effect. As to whether Street Cred is meant to add bonus dice, we need errata to be sure but I honestly doubt this is the case, since they not only switched away from dicepool modifiers quite a bit and only the table still contains the likely-archaic dicepool modifier, but they also stopped mentioning a restriction on how big the bonus can be, which seems far more fitting for an intended pure limit-increase.