In my experience, there is strong anecdotal evidence for an inverse correlation between the strength of a person's religious conviction and the variety of their religious experience. Most of the people I have known with deeply held religious convictions of truth and certainty have a very small range of religious experience. Be they Christian or Muslim, they typically have not explored or practiced any religious ritual outside of the one to which they have a strong commitment. It's analogous to someone who thinks a Chevy is the best car in the world but has never driven any other brand. It's not just an individual issue, as very few of the top seminaries in the countries require their students to study religions other than the one to which they are committed.
The Christians or Muslims I know who have personally experienced other religions, hold the doctrines and rituals of their own religion quite loosely.
These facts appear to confirm the hypothesis that religion is largely a group bonding phenomenon.

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1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13