The accusative with infinitive functions practically as a subject after the verbs and phrases used impersonally: fama est, notum est, bonum est. We use quod to express the cause after the verbs of emotion (gaudeo, doleo, laudo, gratias ago, aegre fero, irascor, accuso etc). This cause may also be expressed by the accusative and infinitive construction.
Quod can also stand with the subjunctive mode if the speaker wants to express the personal reason, not real reason, something that could be...
So both your sentences are correct and both are just fine for either traditional and classical latin. In later latin (lingua vulgaris) quod took place of all accusative with infinitive constructions not only after the verbs and phrases expressing emotion.