If you believe the OT is of equal weight as the NT, do you believe in an eye for an eye (Exodus 21:24-25) or turn the other cheek (Matthew 5:38-42)?
Should we stone a man who works on the sabbath (Exodus 31:15) or is the sabbath made for man (John 5:16-17)?
Should we stone a woman caught in adultery (Leviticus 20:10) or should we practice forgiveness and mercy (John 8:3-11)?
I cannot follow you that the OT is equally as authoritative as the new. I only provided a few examples of the differences between the two but I could provide a lot more. The New Testament supersedes the Old. Otherwise we are left with the conundrum of either practicing judgments of death (according to OT law) for every infraction; or practicing mercy for the same infractions according to the NT, never knowing which takes precedence. They are not of equal weight. Someone who believes the Torah and the Tanach is the last word of revelation from God is a Jew not a Christian. Someone who believes that Jesus Christ and the New covenant is the last word of revelation from God is a Christian.
Some verses to consider:
31 "The time is coming," declares the LORD,
"when I will make a new covenant
with the house of Israel
and with the house of Judah.
32 It will not be like the covenant
I made with their forefathers
when I took them by the hand
to lead them out of Egypt,
because they broke my covenant,
though I was a husband to them, "
declares the LORD.
33 "This is the covenant I will make with the house of Israel
after that time," declares the LORD.
"I will put my law in their minds
and write it on their hearts.
I will be their God,
and they will be my people.
18For there is verily a disannulling of the commandment going before for the weakness and unprofitableness thereof.
19For the law made nothing perfect, but the bringing in of a better hope did; by the which we draw nigh unto God.
Hebrews 8:7-9, 13
7For if that first covenant had been faultless, then should no place have been sought for the second.
8For finding fault with them, he saith, Behold, the days come, saith the Lord, when I will make a new covenant with the house of Israel and with the house of Judah:
9Not according to the covenant that I made with their fathers in the day when I took them by the hand to lead them out of the land of Egypt; because they continued not in my covenant, and I regarded them not, saith the Lord.
13In that he saith, A new covenant, he hath made the first old. Now that which decayeth and waxeth old is ready to vanish away.
2 Corinthians 3:5
6He has made us competent as ministers of a new covenant—not of the letter but of the Spirit; for the letter kills, but the Spirit gives life.
7Now if the ministry that brought death, which was engraved in letters on stone, came with glory, so that the Israelites could not look steadily at the face of Moses because of its glory, fading though it was, 8will not the ministry of the Spirit be even more glorious? 9If the ministry that condemns men is glorious, how much more glorious is the ministry that brings righteousness! 10For what was glorious has no glory now in comparison with the surpassing glory. 11And if what was fading away came with glory, how much greater is the glory of that which lasts!
12Therefore, since we have such a hope, we are very bold. 13We are not like Moses, who would put a veil over his face to keep the Israelites from gazing at it while the radiance was fading away. 14But their minds were made dull, for to this day the same veil remains when the old covenant is read. It has not been removed, because only in Christ is it taken away. 15Even to this day when Moses is read, a veil covers their hearts. 16But whenever anyone turns to the Lord, the veil is taken away. 17Now the Lord is the Spirit, and where the Spirit of the Lord is, there is freedom. 18And we, who with unveiled faces all reflect[a] the Lord's glory, are being transformed into his likeness with ever-increasing glory, which comes from the Lord, who is the Spirit.
16"No one sews a patch of unshrunk cloth on an old garment, for the patch will pull away from the garment, making the tear worse. 17Neither do men pour new wine into old wineskins. If they do, the skins will burst, the wine will run out and the wineskins will be ruined. No, they pour new wine into new wineskins, and both are preserved."
I hope this is suffices to show that the Old Testament (remember covenant and testament are the same word in Greek and Hebrew) is not of equal weight to the new.