Do you see what you're doing here? What Christ accomplished is indeed that which spans all of time, but the doorways (dispensations) to that accomplished work are not all the same.
Peter preached this [the statements in brackets are my comments]:
Acts 2:37-38
37 Now when they heard this, they were pricked in their heart, and said unto Peter and to the rest of the apostles, Men and brethren, what shall we do?
38 Then Peter said unto them, Repent, and be baptized every one of you in the name of Jesus Christ for the remission of sins, and ye shall receive the gift of the Holy Ghost.
Paul, however, preached this:
1 Corinthians 15:1-4
1 Moreover, brethren, I declare unto you the gospel which I preached unto you[Not a summary, but that which he preached as THE gospel to Gentiles], which also ye have received, and wherein ye stand;
2 By which also ye are saved [This is an absolute statement, not something anything can be added to from any other narrative for salvation.], if ye keep in memory what I preached unto you, unless ye have believed in vain.
3 For I delivered unto you first of all that which I also received, how that Christ died for our sins according to the scriptures;
4 And that he was buried, and that he rose again the third day according to the scriptures:
These statements were not made days or even a year apart from each other, but rather YEARS apart, with much happening in between.
Notice that Paul did not repeat the Kingdom Gospel preached by the twelve, but ONLY faith in the death, burial and resurrection on the third day, no water baptism for remission of sins, just grace through faith.
So, the question remains unanswered...why claim similarity when one can clearly see such a claim is false?
Was Paul guilty of the sin of omission? If so, then that guilt ties right back into God Himself if Paul was right about ALL of scripture being inspired by God. Are we now in good standing as accusers of God who is not guilty of any falsehood? Is it not more likely that PEOPLE are wrong when seeing the dichotomy between their claims and what's actually written? Are not those individuals wrong who claim what is contrary to what's written? Where did Paul ever claim that water baptism did anything in relation to sins being remitted through getting wet through dunking in water?
Some even go WAY too far by claiming that Peter was talking about "spiritual" baptism, which is not at all consistent with the words spoken. Nobody can go and BE spiritually baptized as an act in and of itself, which was given that under the Kingdom Gospel through the laying on of hands as that spiritual baptism through which THEY received Holy Spirit. Under the Gospel of Grace, salvation is instantaneous as is spiritual baptism and filling of Holy Spirit. Paul stated no command for anyone to go and BE baptized. He didn't need to command such.
Then the nay-sayers point at those who were under the Kingdom Gospel questioned by Paul as to if THEY had received Holy Spirit and yet stated that they had never even heard if there be such a One as Holy Spirit. They were under the Kingdom Gospel, which did indeed require water baptism and laying on of hands for receiving Holy Spirit.
This almost always causes brain farts in the minds of those fully indoctrinated into the Westernized system of pure religion as a mixture of human traditions from people's who did not originate from the biblical foundations of Eastern Judaism.
So, granted, many will still continue to parrot that imaginary similarity regardless of the textual distinctions, believing whatsoever they WANT to believe, giving greater weight to the false teachings of their pastors, parents, friends, et al. The text is so clear, which puts this all far outside the realm of personality and dogma.
Hope this helps to get some thinking more deeply about the paradigms of typical, Western thinking and pride.
MM
