After a long familiarity with the music of Mahler, discovering the Hans Rott Symphony in E is less like a conscious reach into memory than an unforeseen flashback. For all its evocations and anticipations, and inspite of some formative shortcomings, this is music with its own personality, in a way comparable to Mahler's formative cantata, "Das Klagende Lied." As a work of daring and originality in its own right (if not necessarily a masterpiece), the symphony is definitely enjoyable, especially in passages where Rott is least connected to predecessors or Mahler-to-come.
If there was a reason for Mahler to consider Rott the "father of the modern symphony," it may have been how he pushed at the edge of the distinction between the composer's music and the "musique concrete" of the world--especially noticeable in the scherzo. Rather than seemlessly synthesize these different worlds as Brahms did, Rott and Mahler leave the inconsistencies exposed, even highlighted. I suspect this is the main principle of inclusiveness Mahler had in mind when he said a symphony must be "like the world."
Many commentators have found passages in Rott that anticipate Mahler, but the notes by Eckhardt van den Hoogen also fill in a missing biographical link. It is well known that Mahler saw a score of the Rott symphony around 1900. The notes for the recording point out that Mahler had also performed a version of the work on piano in the early 1880's. That's early enough to influence Mahler's 1st Symphony, and maybe even early enough for this favorite people to influence--in a more subtle way--the E Major Symphony of his teacher, Anton Bruckner.
More interesting than pinpointing where Rott sounds like Mahler is defining the affinity between the two, which has a good deal to do with pushing at boundaries. It's easy enough to hear the resemblance between part of Rott's long finale and the long finale in Mahler's 2nd Symphony--music seemingly perched on the edge of another world. Even more interesting is how the void practically emptied of music (just before the "Aufersteh'n" chorus) re-emerges in late Mahler, especially in the twilight recitativ before a glowing arioso section of "Der Abschied." This isn't a matter of quotation, but about what's under a composer's skin, something that extends from first works to the last.
Listening to Rott also sheds a light on what makes Mahler different. Mahler supposedly complained about how much his composing suffered (at least quantitatively) because of all the time he spent conducting, especially conducting opera. But that time might also have enriched his sense of the dramatic, lyrical and comic elements that are common to opera and instrumental music (as with another of Mahler's idols, Mozart). Even listening to Mahler's 1st Symphony after Rott shows how the more famous composer was more comfortable with the dynamics of drama, as if he had been through the drill many times before as a conductor.
With only fragmentary exposure to other recordings, I would have to say the strongest competition for the Davies performance would be the BIS recording with Leif Segerstam. Davies's orchestra has an edge over the players on the commonly available (in US) Hyperion reissue, though the inclusion of Rott's earlier "Pastorales Vorspiel" might be a bit of a come-down from the symphony.