Apriel-v1.5-15B-Thinker vs GPT-5.3 Codex (xhigh): Which AI Model Is Better?

Updated March 26, 2026· Based on independent benchmark data

Quick Verdict

GPT-5.3 Codex (xhigh) leads in intelligence with a score of 54.0 vs 28.3. For speed, Apriel-v1.5-15B-Thinker wins at 141 tok/s vs 72 tok/s.

Head-to-Head Comparison

Metric	Apriel-v1.5-15B-Thinker	GPT-5.3 Codex (xhigh)
Intelligence Score	28.3	54.0
Coding Score	18.7	53.1
Math Score	87.5	N/A
Speed (tok/s)	141 tok/s	72 tok/s
Latency (TTFT)	0.20s	83.91s
Input Price / 1M tokens	Free	$1.75
Output Price / 1M tokens	Free	$14
Context Window	N/A

Detailed Analysis

Intelligence & Quality

GPT-5.3 Codex (xhigh) outperforms Apriel-v1.5-15B-Thinker on the intelligence index with a score of 54.0 compared to 28.3. For coding tasks, GPT-5.3 Codex (xhigh) has the edge with a coding score of 53.1 vs 18.7.

Speed & Latency

Apriel-v1.5-15B-Thinker generates output significantly faster at 141 tok/s compared to GPT-5.3 Codex (xhigh)'s 72 tok/s, making it 1.9x faster for streaming responses. Time to first token is 0.20s for Apriel-v1.5-15B-Thinker vs 83.91s for GPT-5.3 Codex (xhigh), which affects perceived responsiveness in interactive applications.

Pricing

Apriel-v1.5-15B-Thinker is completely free, while GPT-5.3 Codex (xhigh) costs $1.75/1M input tokens and $14/1M output tokens.

Best Use Cases

Choose Apriel-v1.5-15B-Thinker when you need faster output (141 tok/s). Choose GPT-5.3 Codex (xhigh) when you need higher intelligence (54.0), stronger coding performance (53.1).

Choose Apriel-v1.5-15B-Thinker if:

✓You need faster throughput (141 tok/s vs 72 tok/s)
✓You want lower latency (0.20s vs 83.91s TTFT)
✓You want zero cost (Free vs paid)

Choose GPT-5.3 Codex (xhigh) if:

✓You need higher intelligence (score: 54.0 vs 28.3)
✓You prioritize coding performance (score: 53.1 vs 18.7)

Frequently Asked Questions

Is Apriel-v1.5-15B-Thinker better than GPT-5.3 Codex (xhigh) for coding?

GPT-5.3 Codex (xhigh) scores higher on coding benchmarks (53.1 vs 18.7), making it the better choice for programming tasks.

Is Apriel-v1.5-15B-Thinker faster than GPT-5.3 Codex (xhigh)?

Apriel-v1.5-15B-Thinker is faster, producing output at 141 tok/s compared to GPT-5.3 Codex (xhigh)'s 72 tok/s.

Can Apriel-v1.5-15B-Thinker process images?

No, Apriel-v1.5-15B-Thinker does not support image input. Neither model supports image input.

Should I use Apriel-v1.5-15B-Thinker or GPT-5.3 Codex (xhigh)?

It depends on your priorities. GPT-5.3 Codex (xhigh) scores higher on intelligence (54.0), but Apriel-v1.5-15B-Thinker may be better for specific use cases like cost savings or speed-critical applications.

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View Apriel-v1.5-15B-Thinkerdetails →View GPT-5.3 Codex (xhigh)details →Full pricing comparison →

Data last synced: March 26, 2026