Rather, though still attempting to "cold logic", I will base my argument against Christianity from the textual basis it espouses as its own foundation. It is remarkable to me that Mr. Russell whose work in the logical foundations of arithmetic and axiomatic theory was unable to find the inconsistency inherent in the Christian system.
I understand that Christianity takes the position that the "Old Testament" is useful mainly as a moral guide and a "fire and brimstone" counterpart to Jesus's messages of love and mercy. The Ten Commandments and patriarchal narratives are OK, but kashrus laws and circumcision practices are no longer necessary. As odd as this "pick-and-choose" basis of a religion is, Christianity still incorporates the book of Devarim (Deuteronomy) as the Word of G-d.
The smoking guns is found in this week's parashah, Re'eh. The first gun, as it were, is found at the end of the second aliya where the general principle of Jewish observance is recounted:
Safeguard and hearken to all these words that I command you, in order that it be well with you and your children after you forever, when you do what is good and right in the eyes of HASHEM, your G-d. (Deut. 12:28)
While a modern Protestant might point to the last phrase "do what is good and right" as the ethical imperative to live "a good, Christian life" regardless of observance of the laws, Rashi puts the emphasis on the first two phrases. The first phrase, says Rashi, implies that one has to safeguard what one knows by reviewing it and committing it to understanding; thereupon one can then hearken to the commandment by performing it correctly. The next phrase "all these words that I command you" says Rashi teach that all of the mitzvos, whether obviously important or seemingly minor, should be treated equally (cf. Pirke Avos 2:1), blatantly refuting Christianity's customized choice of "applicable" laws.
In the next aliya, the Torah goes on to declare its own completeness. Here, we are not referring to mathematical or logical completeness of Russell or Gödel. Clearly, there are certain situations in life which are not specifically touched upon in the written Torah or even legislated by the Rabbis in the Talmud. Rather, Moshe exhorts the Israelites:
Everything I command you that you shall be careful to do it. You shall neither add to it, nor subtract from it. (Deut. 13:1)
The aliya then goes on to speak about the dangers of and punishments for a false prophet. The Sages relate in Sanhedrin 89a that anyone, even one that was previously confirmed to be a true prophet of G-d, is automatically discredited if he claims that any commandment of the Torah should be permanently repealed. Clearly even without the Talmudic extension, Christianity paradoxically acknowledges that Deut. 12:28 and 13:1 were at one point valid but somehow, despite their textual warnings, have been superseded and abrogated by the words of some new prophet.
I cannot vouch for others' justifications for not being Christian, but for me it lies in these contradictions. Of course I can understand that ex post facto, if I were a Christian, these contradictions may be easier to stomach. But that makes a rather flimsy basis for leaving the Jewish faith.