T
he Catholic Church and the Orthodox Church are truly, on the scheme of all the world religions, extremely similar. Probably 95% of their doctrines are virtually identical, and while their prayers and liturgies are distinct, they echo and reinforce one another at every turn. It's sometimes said that the two are basically the same church, but with different spiritual emphases. The simplification is that the Roman Church is focused on the rational side of the faith, while the Eastern Church pays more attention to the mystical.
This is just a simplification, however. I'm a Catholic, and a pretty cerebral one at that, but I'm far more interested in the mystical experience of Christ than the sort of Scholastic reasoning about the divine nature that crops up a lot amongst the Dominicans. Sometimes Catholics get accused of being legalistic, or too rigorous in their definitions and codes, but actually I find this tendency to be extremely helpful in my spiritual life, and in a sense brings the mystical closer.
Confession is a good example. The Catholic Church differentiates between venial and mortal sins -- those trespasses which harm our relationship with Jesus, but do not represent a true sundering; versus those that, by their nature, mean we have turned our backs on the Lord. Giving me this framework, even if not infinitely precise, on which to understand my wrongdoing actually brings me closer to God -- it helps me to develop a stronger sense of shame and a desire for reconciliation and penance, and sharpens the relief of mercy that God gives the penitent. Basically any time the Church is accused of "legalism", I think there's a very good spiritual explanation for the appearance, and that the substance turns out to be very sage indeed.