This is a touchy, and unfortunitely unclear-cut, topic. Here is why: Both of these entities, (RCC and SDA), hold to doctrinal beliefs that are opposed to essential salvific teachings as seen in Holy Scripture.
How is this so? Both preach a differnt Gospel, have a different savior, honor men before God, and require strict adherence to the mandates of their own "faith" or "church" without the ability of the member to openly question.
1) a different gospel and savior: Gospel = Good News. According to Scripture the Good News is that although man is naturally and voluntarily in rebellion against God, God, in His loving-kindness became man in the second person of the trinity,(the Son: Jesus the Christ), and lived a perfect, sinless life before offering Himself up freely to God as a sacrifice and atonement for the forgiveness of sin to all who believe on Him. The gospel message is made effective in men's hearts through the regenerative work of the Holy Spirit and repentance is the fruit of the faith given to men by Him. Justification is granted by God to all who are in Christ through faith and forgiveness of all sins is granted in Christ because of His effective, once for all, sacrifice made. The propitiation of forgiveness is guaranteed as Christ, our high priest, is our continual effective atonement. Sanctification and righteous works will follow, but by NO work does anyone recieve favor from God. It is His act of unconditional grace that imparts devine, unmeritted favor.
Everything just stated is Scriptural. I encourage all to look it all up for yourself and reprove me by Scripture if I misspeak.
RCC gospel: justification comes through faith and the sacrements. Mediation to God comes through the church in the form of it's clergy, Mary, and saints. The mass must be kept as a continual re-sacrifice of Christ for sins. Assurance of salvation is only guaranteed, if that, through works of service towards the RCC as an entity.
SDA gospel: Jesus is Micheal, (an angel...yes, archangel, but an angel nonetheless). Salvation is by grace through faith, and seeking continual forgiveness of every single sin, and an adherence to SDA doctrine, i.e. tithing, saturday sabbath keeping, obstaining from foods, and the acknowledgement of Ellen White as God's prophet. They WILL and HAVE gone as far as to say if you do not keep the saturday Sabbath you carry the mark of the beast and are not saved.
2) honor men before God: We are warned continually throughout Scripture of the dangers and heresy of adhering to man worship or the following of false prophets. This is how the two organizations stand up:
RCC, man or God?: Jesus said, "call no man one earth your 'father', for you have one father, he who is in heaven." The RCC teaches the Pope is infallible, even over the Scripture and its truths! The RCC teaches it's adherents to seek out men, (both living and dead, i.e. priests, saints, Mary), for intercession instead of relying on the finished work of our High Priest, Jesus. The RCC expects adherence to their traditions over Biblical doctrine. They claim that as the Pope, a sinner, is infallible, that he has the power to interpret Scripture and codify tradition as Holy Doctrine.
SDA, man or God?: Jesus said, "Many will come in my name, saying, 'I am the Christ', and decieve many". The Bible never makes allowance for false prophets...never! Never does God predict through a true prophet and have it not come to pass...never! Yet the SDA organization required an adherence to the teachings of Ellen (E.B.) White who has been proven by her own words to be a false prophet. Her false prophesies still exist and are attainable, (her husband of all people preserved them to show her to be a false prophet). In light of this the SDA leadership has never corporately denounced her and still teaches her opinions as if she truly were a prophet. She went so far as to blame God for her failed predictions, yet they stick to her and her teachings in spite of Christ's warnings.
3) They require strict adherence to their own mandates without room for doubt or question:
RCC, dogma or doctrine: Refer to Vatican II wherin it states plainly that sound doctrine is composed of Holy Scripture and Church Tradition. In practice they trump Scripture with tradition every time. They have removed the second commandment from the Decalogue, and this is obvious by their promotion of relics and idols: the toes on the statue of St. Peter, (Zeus), at the Vatican have been kissed off! They instituted and sanctified sunday as the Sabbath. They require strict adherence to the eucharist. They, not Scripture, teach transubstansiation. They teach penance not repentance, purgatory, (nowhere in the Bible), they sanctified Easter and Christmas, Lent, Day of the Dead, All Saints Day. These are traditions, not Scripture, and they teach they have the right to do this. They teach the Holy office of Peter, veneration of saints, indulgences, and that a man, (other than Christ Jesus, Lord of ALL), may give forgiveness of sins!!!
SDA, dogma or doctrine?: Back to Ellen White. Her teachings of food abstinence is an integral part of their tradition. When one is baptized within the SDA organization they are baptized more into that entity than the body of Christ. This is because they believe they are the true remnant body of Christ. Upon baptism there are creeds that must be affirmed to the SDA entity, and this goes beyond ecclesiology, but these affirmations are intended to be a sign that if one does or does not adhere to their traditions or teachings that this is a clear indication of whether or not that person is in Christ. They have a lot to say against the RCC and Papacy, but at the end of the day they are doing some of the same things. They make the SDA organization and teachings of E.B. White the standard mark of salvation. Think not? They teach if you don't keep the saturday Sabbath as they dictate that you have the mark of the beast. They teach that to be a new creation in Christ involves tithing to the SDA entity, as opposed to cheerful giving as Christ said: to the poor. They do not allow for repudiation to their doctrines, (handed down by Ellen White), just as the RCC does with Canon Law.
Some may think the last part there about the SDA's dogma is a bit unfair, but the problem there is the subtlty of it. The RCC is very bold, "This is our doctrine. We changed it. We have the power to do so." They aren't shy about that. The RCC teaches they are Mother Church, all outside her are heretics. The thing is, so do the SDAs in a far morw subtle way. In fact, the SDAs use the RCC as their continual smoke-screen to hide their own apostacy.
Apostacy??? Yes, I am afraid so. The very Bible itself condemns both belief systems as apostate. And who am I, the perfect voice of truth? No. I am a sinner. I am a fallible man who's faith is in Christ alone and His promises found in His Word. I affirm the truth of God's Word though I often misunderstand it. Does this mean I can't understand the doctrines I just spoke of? No, and yes. I need the Holy Spirit to constantly correct and instruct me. I need the members of the Body of Christ to help me in my walk and faith. The members of His Body have no denominational name-tag. There are some in the RCC and SDA organizations which the Spirit will lead out of there. The Spirit has led me away from many false teachers and teachings.
The leaders of both the RCC and SDA organizations often speak truths, but it is not the truths they speak that I take issue with, no, its their insistence that we pledge allegiance to a fallible, faulty system contrived of man over and above the Lord Jesus Christ and His Word.
Incidentally, I observe Sabbath from Friday evening to Saturday evening, not because I believe only those who are saved do, but because I see it in Scripture as unchanged and a joy and honor to my creator. I confess my sins continually, but I never worry that the ones I forgot will be held against me: Christ forgave them all, now and forever. I hate abortion as the Catholics do and believe the charitable acts of both the RCC and SDAs are commendable and very helpful to the poor and needy. My hat is off to both of them for that. But let us remember, our allegiance is to Christ and not an entity, whether it calls itself a church or whatever it calls itself. He loves us and gave Himself up for us. God bless you all.