I seriously do believe that The Telling and Phase One are the 2 finest episodes of TV. If I really had to choose between them, I'd say Phase One was a little better. But I do understand why people prefer The Telling.
Well, first of all, both were true gamechangers. Phase One ended SD 6 and the allience, basically a 34 episode arc. The Telling topped that off by simply rebooting the show(Vaughn married, Dixon cia director, Jack locked up, etc), and taking it into a diff direction(search for the past).
Secondly... after I watched Phase One, apart from the "WTF" last minute, I really couldn't highlight a scene that made the episode what it is. It was perfectly put together, everything was in the right place, every single moment was crucial.
While, The Telling was a bit more "old fashioned" . It is so good because of certain scenes and moments. Irina telling Sydney about the prophecy, then jumps. Jack captured by Sloane, and The Telling is built. Will realizing who's the double. The big fight(and the ending).