Short answer / recommendation
For serialized podcast narration that must sound human and remain consistent across seasons: prefer a dedicated TTS provider (ElevenLabs) for final production, and use ChatGPT voices only for fast prototyping or internal read-throughs. ElevenLabs gives better realism, finer prosody control and stable voice IDs you can freeze; ChatGPT is convenient for script-to-audio tests but currently lags in long-form naturalness.

Why (quickly)
- Audio realism & prosody: ElevenLabs typically produces more natural, expressive long-form narration and supports voice cloning and fine adjustments (pace, breathing, emphasis). That matters when listeners expect a human-feeling narrator for hours of episodes.
- Consistency: ElevenLabs lets you lock a voice_id/voice model and version it, which is critical across seasons. ChatGPT’s voices may be updated or less controllable for exact reuse.
- Workflow & cost: ChatGPT is great inside an editorial loop (quick reads, alternative phrasings) and may be cheaper for prototypes; ElevenLabs is better as the final step when you care about production quality and repeatability.

Decision criteria (pick the most important factors for your show)
- Output quality (realism, breath, emotion)
- Consistency across seasons (can you freeze/export the exact voice?)
- Accent and locale support (native-sounding accents you need)
- API/automation for batch rendering (episode-scale production)
- Cost per minute and licensing (clone rights, commercial use)
- Editing control (SSML, prosody tags, time-stamped segments)
- Team skill level (audio engineering vs. non-technical)

Practical checklist to implement now
1) Choose & lock voice: pick a final voice and save its model/version/voice_id. Archive voice sample and settings.
2) Create a narration style guide: tone, pace (wpm), pauses, filler usage, handling of names/credits. Use examples.
3) Tag scripts consistently: insert SSML or proprietary prosody markers for emphasis, pauses, and breaths.
4) Batch render: produce per-episode segment files (not one huge file) to simplify edits and replacements.
5) Post-process consistently: apply the same chain—noise reduction, EQ, de-essing, dynamic leveling, and final loudness (-16 LUFS for stereo podcast is common). Use a DAW or batch tool like Auphonic/iZotope.
6) Version control & backups: store raw outputs, processed masters, and the script that produced them.
7) Test accents and named-entity pronunciations early; use phonetic overrides if needed.

Best-for / Avoid-if
- Best-for ElevenLabs: serialized long-form narration, voice cloning to preserve host voice, shows that need repeatable, human-feeling reads and per-phrase prosody control.
- Avoid ElevenLabs if: your budget is tiny, or you only need quick internal prototypes.
- Best-for ChatGPT voices: fast script read-throughs, iterative script editing, and teams already centered in the ChatGPT workflow.
- Avoid ChatGPT voices if: you need final-broadcast-quality narration or an exact frozen voice across many seasons.

Notes on team/scale/rights
- Small teams or single producers: ElevenLabs for final renders; ChatGPT for drafts.
- Large teams: enforce the style guide, centralize rendering, and assign one person to maintain voice/versioning.
- Legal: confirm commercial/clone rights and keep consent records if you clone a human voice.

If you want, I can outline a short SSML/prosody template and a post-processing chain tuned for podcast narration. I’d recommend starting with a locked ElevenLabs voice for season 1 and using ChatGPT only as a drafting tool.