Perhaps the reason for different religions is that different people from different cultures and backgrounds need to go on a journey of enlightenment coming from different levels of progress in the latter.
Various religions you could say teach various concepts about enlightenment. Some religions focus on the introduction of god (evangelical), others focus on the relationship with this God, others focus on the christian as a conqueror, others focus on raising conciousness.
All have different purposes depending on the evolution of a person's spirit within. Hence religion hopping is happing more often. Eventually there will only be the need for one religion...the religion of enlightenment.
How we should spread religion is perhaps less important than the need for a person to engage in a spiritual journey of some kind, and ultimately through the intelligence of the universe that person will be born into a culture or environment where they will come into contact with a religion that can set them on this path.
I believe that the Buddaism is the religion that deals mostly with abdicating one's ego. A religion for maturity in spiritual matters. It is silly that different religions fight over scripture and stuff like that. All it is doing is fueling and strengthening ego. If someone is involved in a church that is not willing to accept that someone else out there could perhaps have more answers than they do, then they are inhibiting a person's spiritual growth and teaching them to hold on to their ego's when infact the loss of ego is what is most important for spiritual growth.
Heneni