Intrinsic value of the Mass infinite
Fr. Chad Ripperger, in his Summer 2003 Latin Mass Magazine article "Merit of a Mass", argues that Masses using 1962 Missals and earlier have greater extrinsic merit, while their intrinsic merit (Christ's infinitely meritorious sacrifice) is the same. He quotes Pohle, J. (1911). Sacrifice of the Mass. In The Catholic Encyclopedia:
we must also sharply distinguish between the intrinsic and the extrinsic value of the Mass (valor intrinsecus, extrinsecus). As for its intrinsic value, it seems beyond doubt that, in view of the infinite worth of Christ as the Victim and High Priest in one Person, the sacrifice must be regarded as of infinite value, just as the sacrifice of the Last Supper and that of the Cross. […] But when we turn to the Mass as a sacrifice of impetration and expiation, the case is different. While we must always regard its intrinsic value as infinite, since it is the sacrifice of the God-Man Himself, its extrinsic value must necessarily be finite in consequence of the limitations of man. The scope of the so-called "fruits of the Mass" is limited.
Extrinsic value of the Mass
Pohle expands upon this in The Sacraments: A Dogmatic Treatise (vol. 2): The Holy Eucharist, part 3, ch. 3, §2.1 "Value of the Mass":
As regards the extrinsic value of the Mass, we must first of all distinguish between sacrifices of praise and thanksgiving on the one hand, and sacrifices of impetration and propitiation on the other. The first two are directed to God alone and cannot be applied to man, and hence a sacrifice of praise and thanksgiving offered by the Son of God Himself (in the name of humanity) must be infinite, since God cannot but take infinite pleasure in the praise and thanksgiving of His only-begotten Son.
b) The case is different with sacrifices of impetration and propitiation.
α) Theologians generally4 agree that in itself (in actu primo) the Mass, as a sacrifice of impetration and propitiation, has infinite power, because impetration and propitiation performed by the God-man must have the same infinite value as praise and thanksgiving, though they may not attain their full effect on account of the limitations of human nature. It follows that intensively (intensive) the external value of the Mass as a sacrifice of impetration and propitiation can be but finite. This is confirmed by experience, and also by the fact that the Church allows many Masses to be offered for the same purpose. We may fairly ask, however, whether in its application (in actu secundo) and extensively (extensive) the value of the Mass is also merely finite. Or, to put it somewhat differently,—Can the value of the Mass, which is intensively finite, be applied to an unlimited number of persons in such a manner that its efficacy is in no wise diminished? Or do the individual beneficiaries share in the fruits pro rata? Rather than answer this question in the negative, many theologians prefer to hold that the Mass is of infinite value also extensive, and that the amount of the fruits each beneficiary receives, varies in proportion to his piety, worthiness, and devotion, in short, depends on “the work of the agent” (ex opere operantis). Surely, indeed, he would be a poor Christian who would expect wonders from the Holy Sacrifice of the Mass in spite of his own indifference.5
β) Nevertheless, the question must be answered with a distinction.6 In addition to the active there are also passive participators in the Sacrifice of the Mass. These are the persons in whose favor,—it may be without their knowledge and against their wishes,—the Holy Sacrifice is offered. As regards the active participants, i. e. the celebrating priest and the attending faithful, the distributive value of the Mass does not depend on the number of those who take part in it. If this were the case, it could be truly said that the fewer the people who attend, the greater the fruits derived by those actually present. But this is contrary to the mind of the Church and the belief of the faithful. Each active participant receives as much of the fruits of the Mass as his personal worthiness and devotion entitle him to. It is not possible to assign a definite limit.
4. With but few exceptions, among them Bellarmine, De Eucharistia, VI, 4.
5. See No. 2, infra.
6. Cfr. Suarez, De Eucharistia, disp. 79, sect. 2.