Well, let's see. This is what you wrote and what I replied to--
Ah, so I guess you mean that you asked about the right CHURCH, as opposed to right actions in themselves.
The OP says nothing about right actions. My pure questions is on the benefit of knowing the right doctrine, which means being in the right church.
If so, there is no particular benefit in one's membership and certainly not in this life. Those churches that insist that there is, however, do so on one of two bases. Either they hold that only one church is a real church and God will disapprove of all others along with their adherents
I don't think your heart is in this posit, so I won't challenge you to argue how one church is superior to others but gets no reward for being better.
OR ELSE it is because, on some doctrines at least, the difference between their teaching and that of other church bodies can be a matter of the individual person's spiritual wellbeing. If, for instance, you are led to perform immoral acts because you've been taught that they are actually Godly, your salvation might be compromised and, even if it is not, you wouldn't want to do wrong all the time, thinking it is actually right.
I take you to be in the OR ELSE posit.
Assuming that all the churches in question teach doctrine that is sufficient for salvation, your question of sin is meaningless as we all sin. I commit enough sins that I am aware of to condemn me. God's grace forgives me of them. God's grace also forgives the sins I am not aware of just the same, despite what some argue.
As to a church that has a doctrine that allows sexual immorality, like how homosexuality is accepted in some liberal churches. I have to say this is going to be a challenge to the Church. We should try and reach out to those sinners, but we should not tolerate such open sin as being acceptable to God such that they don't even consider it a sin. For scripture I look to Jesus warning to the church in Pergamum that was had sexual immorality in it, Revelation 2:12-17.
I will give you this argument, but the bulk of doctrinal differences do not revolve around homosexuality, and my OP condition stipulates doctrinal differences that do not affect salvation.
I don't believe in works righteousness either, but these other churches would probably insist that they teach faith and doctrine as much as the performance of good works...and also, that the churches which are strong on faith also do teach that doing good and living a Christlike life style is important as an outgrowth of a lively faith.
So we both agree here, then.
Consider a member of a church that pushes good works as part of salvation spends their entire life doing good things for others, think Mother Teresa or the Salvation Army that has a motto "Doing the most Good".
Will they be better off in heaven because their church convinced them they had to do so many good deeds and they did?