Best AI for essay writing / head-to-head

GPT-5.5 vs GPT-5.6 Terrafor essay writing

The verdict

GPT-5.5 wins, 9488

Same 12 essay writing tasks, marked blind by three rival labs. GPT-5.5 took 4 tasks, GPT-5.6 Terra took 2, 6 tied. Tested 13 Aug 2026.

Where they differed most

The task — Cite honestly

Write a 150-word paragraph on the effects of sleep deprivation on memory. If you reference any study, name it precisely; if you cannot name a real one, say 'no specific study cited' rather than inventing a citation.

GPT-5.510/10
Sleep deprivation weakens memory at several stages. When people stay awake too long, attention becomes unstable, so new information is encoded incompletely and with more errors. Lack of deep slow-wave sleep also disrupts consolidation, the process by which recently learned facts and experiences are strengthened and integrated with older knowledge. As a result, recall the next day can be slower, less accurate, and more vulnerable to interference from similar material. Sleep loss can especially harm working memory, making it harder to hold instru…
Sleep deprivation impairs memory by disrupting attention, encoding, consolidation, and retrieval. When people are tired, they are less able to focus on new information, so fewer details are effectively stored. Insufficient sleep also interferes with hippocampal activity and with the brain’s overnight processing of experiences, weakening both factual and episodic memories. Learning procedures, emotional events, and associations can likewise suffer, although the pattern varies by task and by individual. After prolonged wakefulness, people may fee…

Task by task

TaskGPT-5.5GPT-5.6 Terra
Structured argument58
Essay plan109
Tighten flabby prose910
Hold a word count99
Adapt for the reader1010
Introduction only1010
Steelman the other side1010
Cite honestly105
Fix the structure105
Formal to plain109
Conclusion that adds something1010
Refuse to pad1010

Full receipts: GPT-5.5, GPT-5.6 Terra · judges claude-sonnet-5, gemini-3.1-pro-preview, grok-4.5

Questions people ask

Which is better for essay writing: GPT-5.5 or GPT-5.6 Terra?

GPT-5.5 — it scored 94/100 against 88/100 on our 12-task essay writing suite, winning 4 tasks to 2 with 6 tied. Every answer was marked blind by three judges from three rival AI labs.

How was this tested?

Both models answered the identical published essay writing tasks. Three AI judges from three different labs scored every answer blind against a fixed rubric; mechanically checkable rules (word limits, banned phrases) are enforced by the test harness in code. The raw outputs and judge verdicts are downloadable.

More essay writing head-to-heads: GPT-5.5 vs GPT-5.6 Sol · GPT-5.6 Sol vs GPT-5.6 Terra · GPT-5.5 vs GPT-5.6 Luna · GPT-5.3-Codex vs GPT-5.5 · Claude Sonnet 5 vs GPT-5.5 · Claude Opus 4.6 vs GPT-5.5

Full ranking: Best AI for essay writing · model pages: GPT-5.5, GPT-5.6 Terra