Gamma-ray bursts versus quasars:: Lyα signatures of reionization versus cosmological infall

Lyalpha absorption is a prominent cosmological tool for probing both galactic halos and the intergalactic medium at high redshift. We consider a variety of sources that can be used as the Lyalpha emitters for this purpose. Among these sources, we argue that quasars are the best probes of the evolution of massive halos, while gamma-ray bursts represent the cleanest sources for studying the reionization of the intergalactic medium.