By "climax" do you mean the pinnacle of Symphonic writing, such as orchestration, tonal language, or symphonic form? Or all?
This reminds me of the old debate between Brahms and Wagner (regarding the true descendant of Beethoven) back in the day
I have to admit it is hard for me to vote, because such a "journey" is difficult to qualify in absolute terms. Richard Wagner's tonal language and expressive range (in regards to expansive forms and dynamics ) really opened alot of doors, so to speak. Alot of composers reacted and others, such as Mahler and Bruckner, embraced Wagner's aesthetic.
Brahms was apparently more traditional, but, according to Schoenberg, his work was more radical or "modern" than most...just more subtle rather than extreme.
So it's hard to say really, but interesting to discuss!
I voted for Brahms (in the tradition of classicism) and Mahler (romanticism).
Bruckner is interesting as he seems to be a combination of classicism and romanticism.
I hope I'm making sense