In my opinion, the most you benefit from subtitled anime is Japanese vocabulary.
I will throw a cluster of words (and/or phrases?) I learned and I am sure most of you who probably watched anime for years would recognize many. These are only some:
baka, demo, nande, wakateru, ame, yume, bakemono, wakarimasu, wakarimasen, soriyori, nani, chigaimasu, mi-te, hikari, aka, kuro, shiro, ni-ge-te, hayaku, watashi, boku, nii-san, ne-san, otoko, unna, kanojo, otosan, okasan, obachan, ikkiimaasu, kso, shiksho, matte, toma-re, koros, shinjite, kanashimi, yasashi, futari, anatawa, minna, kisama, dareka, taicho, hi-me, sekai, sai-kyo, honto, yada, naniyo, jodan, da-me, kirai, ai, ski
Oh, some include honorifics but we all know them, san, kun, chan, sama, dono, sensei, senpai, kohai, bozu and (none)
Anyone who didn't "properly" learn Japanese know these words?