When it comes to examining Christianity, and especially which path to follow upon careful study and prayer, the three "top choices" are: Catholicism, Eastern Orthodoxy, and Protestantism. Protestantism is the least likely candidate, and is to be rejected on various grounds (e.g. no historical continuity before Luther). This leaves Catholicism and Eastern Orthodoxy. The following ten reasons (not necessarily exhaustive) are why I'm not Eastern Orthodox, while not forgetting there is much good in the Orthodox Churches and that they are very close to Catholicism in many ways:
(1) Their leading Bishoprics, Constantinople and (now) Moscow, have no Apostolic Roots. (Where as the Roman Church was founded by the "two most glorious Apostles," Saints Peter and Paul.)
(2) They cannot agree upon a Canon of Scripture - nor does there appear to be a means of infallibly defining one. (e.g. The EO at the Council of Jerusalem in 1672 affirmed the same Canon as Catholics, though I've seen other EO sources denying some of those books.)
(3) They have manifestly defected from basic Christian principles, caving into worldly pressure, for example they allow Divorce and Contraception.
(4) They cannot agree as to whether Catholics have valid holy orders or other valid sacraments - some EO say 'yes', others say 'no'. Some re-baptize Catholics, others do not. And, again, there appears no way of 'officially' settling the issue.
(5) They cannot agree as to whether decrees such as the Council of Jerusalem of 1672 was universally binding - moreover, those EO who deny the authority of the Council of Jerusalem (often because it sounds too "Latin") wont go as far as to condemn it as manifest heresy and an abomination (which it logically should be *if* it teaches heresy and other abominable things).
(6) They cannot agree as to whether "Latin" figures such as Augustine are "saints," or "venerable," or merely confused Christians, or even arch-heretics (nor have I seen any 'official' EO pronouncements for the last option). Further, they generally don't give the Western Fathers as much respect or recognition as they do the Eastern Fathers.
(7) They have not had an Ecumenical Council in over 1,000 years, and this is apparently because they have no objective means of calling and establishing one.
(8) They downplay into virtual irrelevance the strong testimony (be it in Scripture, Tradition, or Patristics) for the Papacy.
(9) They have backed out of agreements, such as the Council of Florence, often with individual bishops overturning the 'votes' of other bishops and Patriarchs.
(10) They have had little influence in terms of evangelization outside of Eastern Europe, where as the Catholic Church originally evangelized (and still dominates) North and South America, Africa, and Asia all centuries ago.
In my experience, when Protestants leave their own denominations for Catholicism or Eastern Orthodoxy, those choosing the latter are often primarily driven by anti-Catholic bias more than a fair and balanced look at the facts and which side offers the better arguments. Though I am Catholic, in fairness I cannot brush aside worthy candidates for the title of "One, Holy, Catholic, and Apostolic Church," and that is why I felt it necessary to give some reasons for my choice. I believe the above reasons are sound and decisive in making the right choice. I realize there are major issues such as the Filioque not (directly) addressed above, but that is because the acceptance of such issues is largely dependent on which side has the true Authority to decide such matters.