[Foolofatook]

I have always seen Elros' decision as a choice for power. He was given the opportunity to rule the great nation of men in its original glory. That sounds pretty good to me. Also didn't Elrond start out as a servant to Gil-Galad. It wasn't until much later that he founded Rivendell. In a way they both chose immortality, Elrond in a physical form, Elros in a figurative form. He got a pretty good deal in the end, maybe even better than Elrond. But that's up for interpretation.