Should Christians use the Septuagint instead of the Masoretic Text?

Neither. That is the short answer — and it is not a soft middle-ground answer. It is what the apostles' own citation practice shows when you work through it verse by verse.

The claim you have probably seen online goes something like this: the Septuagint (the LXX, the pre-Christian Greek translation of the Hebrew Bible) is older and more accurate than the Masoretic Text (the MT, the standardized Hebrew text finalized around AD 600–1000), and the New Testament writers proved this by using the LXX almost exclusively.

Every one of those claims contains real data. And every one of them is overstated.

The LXX is a translation, not a competing original. It was made from Hebrew manuscripts that no longer exist in full — manuscripts that in some places preserved readings the later Masoretic tradition lost. At Isaiah 53:11, four Dead Sea Scrolls manuscripts (1QIsaᵃ, 1QIsaᵇ, 4Q56, 4Q58) include the word "light" (אוֹר, ʾor) as the object of the Servant's seeing. The MT lacks that word. The LXX includes it. Here the LXX is right, and the DSS prove it. At Deuteronomy 32:43, the LXX's "let all the angels of God worship him" is not a creative expansion — 4Q44 (4QDeutᵍ) confirms that the LXX is translating a longer Hebrew original that the MT's tradition shortened. The author of Hebrews quotes it (Heb. 1:6) because it was there.

But the LXX also makes moves the MT does not. At Genesis 3:15 the Hebrew verb שׁוּף (shuf, H7779, meaning "to strike violently, to crush") becomes the Greek τηρέω (tēreō, G5083, "to keep, to guard") — the aggression of the curse is softened. At Proverbs 8:22 a verb of acquiring becomes a verb of creating, a shift that fed the Arian controversy in the fourth century. And at Zechariah 12:10, the LXX translator replaced "they pierced" with a verb meaning "they mocked" — breaking the pattern every other LXX translator had established for the Hebrew root דָּקַר (daqar, H1856).

That last case is where the apostles vote. John cites Zechariah 12:10 at John 19:37 and again at Revelation 1:7 — and both times he uses the standard Greek word for piercing (ἐκκεντέω, G1574), not the LXX Zechariah's mockery verb. He follows the Hebrew against his own community's Greek text. The pre-Christ Hebrew at Qumran (4Q80 (4QXIIᵉ)) preserves the same root דקרו ("they pierced") that the MT carries — the apostles' Hebrew Vorlage matches both the proto-MT and the older Qumran witness.

The apostles were not uniformly LXX or uniformly MT. Matthew quotes the LXX form of Isaiah 7:14 at Matthew 1:23 — one chapter later, at Matthew 2:15, he quotes the MT-semantic form of Hosea 11:1. Of twelve key Old Testament quotations tracked in this study, seven follow the LXX, three follow the Hebrew of the MT, one is eclectic, and one is adapted beyond either form.

The Dead Sea Scrolls showed us, decades before this conversation moved online, that the Old Testament text existed in multiple ancient Hebrew recensions before Christianity and before the rabbis — short forms, long forms, proto-MT, proto-LXX Vorlagen, and independent traditions. Choosing one of those recensions wholesale, against the apostles' own practice, is a category error.

The full study Which Old Testament? works through all eight contested passages with the Hebrew, the Greek, the Strong's numbers, and the NT citation evidence laid out in full.