They are both, in a way, constructs of the human mind.
An interpretation of reality, if you like.
Are they not? Why does the one construct make more sense to you?
Are you saying that Allah exists because people have determined he exists?
If that's the case, then I completely agree.
In fact, I made the same argument for the existence of Jesus about a year ago:
http://www.sciforums.com/showthread.php?t=85618&highlight=historicity
If enough people believe in the historicity of Jesus then, pragmatically speaking, it is true, because there is no real difference in the outcome.
In that sense, I believe all Gods and demons exist.
However, there s a great chasm between pragmatic truth and metaphysical reality.
If you are strictly looking at the Quran in an alegorical sense and Allah as a pragmatic truth, that is something entirely different. In that case, then I agree 100% that the only difference between the Quran and the Pali Canon is a matter of personal value and reason of what the texts taught.
If, on the other hand, when you say you believe in Allah (and heaven and other such ideas contained within the Quran) in the sense that he is a metaphysical reality, then that brings us back to Islam requiring faith, as opposed to Buddhism and the whole point of the man's metaphor in the opening post.