Generally speaking, quality is overwhelmingly more important than quantity. Quantity is also important but there is no comparison between the two. This is because, if the required quality is not present, it really doesn’t matter how much of it we have. For instance, if we serve food to a thousand people, but the food is not fit to eat (maybe it is made with rotten ingredients), it has no value and must be discarded. Similarly, if we pray all day long without regard to how we pray, our prayers are maybe of no value at all.
Mediocrity is ubiquitous. Excellence is rare. In my opinion, it is exponentially more important to focus on the quality than quantity. Particularly when it comes to worship. Making sure our worship is of the highest quality possible is essential. Quality in worship has two primary components. Our worship must be done for the sake of Allah alone. And our worship must be done in accordance with the Sunnah of the Prophet (ﷺ). These two components are mandatory conditions for the acceptance of any worship. Worship done for other than Allah or done in a manner not according to the Sunnah, is rejected. It may even be a cause of humiliation on the Day of Judgment.
In addition to meeting these two conditions, the level of Khushoo & Khudhoo (concentration), Taqwa (God consciousness), humility and love for Allah determines the quality of our worship. If this quality is not there at all, there is hardly any value left in the prayer. The obligation to pray the mandatory prayer is met when a prayer is performed but the rewards that are promised in this world and the hereafter cannot be attained from a prayer that lacks quality altogether. The more effort we put in attaining a better level of our worship, the more quality and hence the more value it is for us in the hereafter.
And Allah knows best.