Having read both the Holy Bible and the Holy Qu'ran, I find nothing that makes any of these kinds of debates necessary. In all my years, I have never, not even once, seen someone change their mind about their religion because someone told them they are stupid/naïve/deceived. If anything, those who have converted to or from Christianity or Islam have done so because they were shown LOVE.
If you can't show love for those who believe differently, you'll NEVER manage to convert them, so even if your secret goal is to convince the whole world to change to your religion, it probably won't happen unless you speak to them kindly no matter what they currently believe.
"Verily, Allah is mild and is fond of mildness, and He gives to the mild what He does not give to the harsh" (hadith)
"An answer when mild is turning away rage" (Holy Bible)
"Do you know what is better than charity and fasting and prayer? It is keeping peace and good relations between people, as quarrels and bad feelings destroy mankind" (hadith)
"The fruit of the Spirit is love, joy, peace, patience, kindness, goodness, faithfulness, gentleness and self-control. Against such things there is no law." (Holy Bible)
There is a verse from the Holy Bible that I think might be a good one to think about, especially when we are tempted to start saying very ugly things about the religion of someone else:
"Finally, brothers, whatever is true, whatever is honorable, whatever is just, whatever is pure, whatever is lovely, whatever is commendable, if there is any excellence, if there is anything worthy of praise, think about these things."
Instead of focusing on the myriad things that we may think are wrong with the religion of someone else, wouldn't it be more godly to focus on those things that we believe their religion does right?