[Lord Elrond]

I apologise for my sarcasim, I didn't literally mean that I was trying to make the point(although I did it poorly) that Tolkien needed a character to continue the line of men. I agree with most of your theories and I am sure that many of them could be correct but when it comes down to it Tolkien had a an elf to continue the tale of the marriage of the two races but he wanted a man to also continue the line so that men and elves would not be wholey estranged in the third age. I am sure stories could and might have been made to explain Elros theory but if they both would have chosen to be immortal it just would not have been as interesting and there would not have been able to be as many options for Tolkien to continue the story with.
I apologise again for the short answer I originally posted and my sarcastic comment about daddy's boy (although children often favor one parent over the other and this could be one of those created stories as to why he chose however it is only a possibility and not the point I was trying to make) but I hope that I cleared up and ask all of you to look at my last statement after explaining myself better. I hope you don't think any less of me and will forget any conclusions you might have come to about me from my last statement.