It is better to believe in the God of the Bible than to believe in Allah

I am not a Muslim, as you asked for, but I used to be before I apostated from the religion some years ago, and I believe I have in my youth gathered enough insight into its teachings to discuss this matter to your satisfaction.What you're doing, is rephrasing what's known as Pascal's Wager for the context of a Muslim and a Christian in quarrel, much the way the French mathematician and theologian Blaise Pascal (1623-1662) phrased it as an argument in such a quarrel between a generic believer and an atheist (or the inner discussion a man doubting these two positions may seek solace in).If reason cannot make certain if God exists or not (and it cannot, the philosopher confessed), yet loss and gain is taken into consideration, then he who believes, if God exists, gains all; if He does not, loses nothing - yet who does not believe, if He does not exist, gains nothing; but if He does, loses all - thus, persuading the thinker, that only belief could possibly be in his gain, and thus the only favourable decision to make.Though I am amused by the cleverness of this idea, it seems clear to me that such a restrained perspective on something which always pretends to be ever-expansive (namely God) does very little honour to the concept - and can, from a mind as admirable in its inventiveness as Pascal's, only be the product of high sentimental confusion.For it becomes clear, if you translate this opposition between belief and disbelief arbitrary, to the specific beliefs of Christianity and Islam, it takes on a very different shape. Sure, we can say, almost naïvely, if either one or the other are correct, where are my odds best. A nice little game, which I will gladly play with you, but you'll have to explain to me first exactly how you can apply this seriously in your own metaphysical/spiritual contemplations.For you would have to take into account all religions, and assuming you cannot solidify on the basis of reason any greater probability for one than any other, the only way of increasing your odds of salvation would be to find, in the largest pool of religions that 'allow' one another, in that the followers of one are 'excused' by the other, as you presume it to be the case with Islam for Christianity, and then to adhere to the least tolerant of them to the others. You could picture it as Euler diagrams (the ones that are popularly used in introductory teaching of formal logic) where one figure or surface is contained in another, so that being in A (for instance, the graces of the Christian faith) also puts you in B (for instance, the graces of the Buddhist faith) but not necessarily the other way about.If you can organize all religions in this way, you can find the one where in the end you have the most chances of being saved in the afterlife. And again, is it not peculiar, and so fitting for the ineptitude to provide fixture of heart, which religions pretend to do, that being saved or not, in this wondrously rational perspective, is entirely on chance dependent? But good luck for creating this chart, for the thousands upon thousands of religions, and the various subtle denominations, and differences of opinion between the followers of each on the specifics of their creed. You'll come to the conclusion, by the very statistical reckoning which you wanted to debate, that any one of them, has only the smallest chance of being the right one. But to get to the intitial question - not to hold you in suspense any longer - if either Christianity or Islam are true, then what are the odds of the adherent of either to be saved? I'm afraid this question, and your very black-and-white assertions concerning it, will also buckle under the theological sophistry and disputes on both sides. To quote against my better judgement, but for the sake of brevity from the Wikipedia page on the Afterlife:"Some Christian believers have come to downplay the punishment of hell. Universalists teach that salvation is for all. Jehova's witnesses and Seventh-day Adventists teach that sinners are destroyed rather than tortured forever. John 3:16 says that only those that accept Jesus will be given eternal life, so the people that do not accept him cannot burn in hell for eternity because Jesus has not given them eternal life, instead it says they will perish."If one reads any random spots of the Qur'an, one realizes that the interpretation of All-Merciful does certainly not entail that he forgives all, and extends no punishment."…Indeed, We have prepared for the wrongdoers a fire whose walls will surround them. And if they call for relief, they will be relieved with water like murky oil, which scalds [their] faces. Wretched is the drink, and evil is the resting place." [Quran 18: 29]"And those who disbelieved will be driven to Hell in groups until, when they reach it, its gates are opened and its keepers will say: 'Did there not come to you messengers from yourselves, reciting to you the verses of your Lord and warning you of the meeting of this Day of yours?' They will say: 'Yes, but the word [i.e. decree] of punishment has come into effect upon the disbelievers.'" [Quran 39: 71]And more of that kind of stuff.I can say, from my own experience with the mainstream Sunni creed - which exempts a small number of extreme Sufis (the equivalent of Universalists) and those who do not reckon the Jews and Christians amongst the disbelievers, since they believe in God, and only disbelieve in Mohammed's prophethood and the divinity of the Qur'an - that the people of the Book, and all other religions, mono- or polytheistic, if they have come into contact with the truth (i.e. Islam) and then rejected it, they will be condemned, and no refuge will be available to them.So I feel confident to say that your chances of salvation, if either of these religions must be true, are pretty equal in both, balancing the orthodox and moderate judgements against one another, going on the idea that none has reasonable preference over the other. But how far we drag this, and how theologically specific we'll get, will be for the remaining rounds to show.