"Why Catholic and not Eastern Orthodox?"
Orthodox churches allow divorce and remarriage, as well as contraception. The teachings of Catholicism make more sense in light of what's been revealed in Sacred Scripture. To quote from the conversion story of Cindy Beck (http://www.chnetwork.org/cbconv.htm):
"Up until 1930, all Christian churches taught that contraception was intrinsically evil and gravely sinful. It was the Anglican Church, at its Lambeth Conference, that first approved the use of birth control. Since that time, every single Protestant denomination and sadly even the Orthodox Church has followed suit, departing from nineteen hundred years of universal Christian belief."
The Orthodox church does not allow divorce or contraception.
The church allows remarriage in cases of adultry. The difference being they don't call it an annulmant even though it is the same set of criteria. It's based on the exact same scriptural reference the Catholic church uses for determining anulmants.
Other Orthodox General Info
Russian Moscow Patriarchiate
General Info Sites:
Anyone familiar with the Orthodox church and Catholic church doctrine will confirm the doctrine in both the Catholic and Orthodox churches is near identical on these topics. Your 'mileage may vary' from parish to parish, however it does in the Catholic church as well.
Further they hold to the Fourth Council definition of primacy:
And the original version of the Nicene Creed:
Best of both worlds! The Catholic Church breathes with two lungs - a Roman Catholic may attend the liturgy or join the parish of an Eastern Catholic Church. It also helps to have a definitive voice at the Vatican ;-D