Dr. Bombay:
Because one of the publishing companies (Baronius) is serving Catholics who are loyal to the Holy See and wish to attend a TLM approved by the respective diocesan authority.
While the other (Angelus) is owned by a schismatic, non-Catholic sect whose main goal is to cause dissension and discord within Holy Mother Church and inflict ever more wounds on the Mystical Body of Christ.
It’s really quite simple. One markets their product to loyal Catholics. The other to prideful dissidents.
That is inaccurate, and hardly fair. I attend a traditional rite parish in Georgia (FSSP priests). We have several items in our church put out by the SSPX. For example, we use The Traditional Roman Hymnal and another, smaller one (forget the name); they are in our pew racks. Our bookstore also stocks both the Baronius missal and the Angelus missal. Every bit of literature in our parish must first have the approval of our very orthodox priests.
Please don’t forget that Rome has said that faithful Catholics who are attached to the TLM may satisfy their Sunday obligation at an SSPX chapel, if their reason for attending is love of the traditional mass as opposed to dissent from church authority. While I don’t doubt that there are “prideful dissidents” in SSPX parishes, I think it’s equally fair to say that there are just as many, or more, in the Catholic Church as a whole, whose dissent is far more damaging to the faith.
As for the missals, I recently replaced my old St. Andrew’s missal with the Angelus Press one. I compared it to the Baronius, and liked it better. The paper quality is lovely and gilt-edged. Also, the print is larger than in the Baronius missal and very clear and easy to read. (This was a big issue to me, since some of the print in my St. Andrew’s missal is teeny-tiny.

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While the Angelus missal does not have a real leather cover, the “leatherette” flex cover it does have is of excellent quality and quite beautiful. All in all, the missal is just a joy to use. While you would not be disappointed in either, I think the Angelus missal is superior.