Phi-3 Mini Instruct 3.8B 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 10.1. For speed, GPT-5.3 Codex (xhigh) wins at 72 tok/s vs 0 tok/s.

Head-to-Head Comparison

Metric	Phi-3 Mini Instruct 3.8B	GPT-5.3 Codex (xhigh)
Intelligence Score	10.1	54.0
Coding Score	3.0	53.1
Math Score	0.3	N/A
Speed (tok/s)	0 tok/s	72 tok/s
Latency (TTFT)	0.00s	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 Phi-3 Mini Instruct 3.8B on the intelligence index with a score of 54.0 compared to 10.1. For coding tasks, GPT-5.3 Codex (xhigh) has the edge with a coding score of 53.1 vs 3.0.

Speed & Latency

GPT-5.3 Codex (xhigh) generates output significantly faster at 72 tok/s compared to Phi-3 Mini Instruct 3.8B's 0 tok/s, making it Infinityx faster for streaming responses. Time to first token is 0.00s for Phi-3 Mini Instruct 3.8B vs 83.91s for GPT-5.3 Codex (xhigh), which affects perceived responsiveness in interactive applications.

Pricing

Phi-3 Mini Instruct 3.8B is completely free, while GPT-5.3 Codex (xhigh) costs $1.75/1M input tokens and $14/1M output tokens.

Best Use Cases

Choose GPT-5.3 Codex (xhigh) when you need higher intelligence (54.0), stronger coding performance (53.1), faster output (72 tok/s).

Choose Phi-3 Mini Instruct 3.8B if:

✓You want lower latency (0.00s 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 10.1)
✓You prioritize coding performance (score: 53.1 vs 3.0)
✓You need faster throughput (72 tok/s vs 0 tok/s)

Frequently Asked Questions

Is Phi-3 Mini Instruct 3.8B better than GPT-5.3 Codex (xhigh) for coding?

GPT-5.3 Codex (xhigh) scores higher on coding benchmarks (53.1 vs 3.0), making it the better choice for programming tasks.

Is Phi-3 Mini Instruct 3.8B faster than GPT-5.3 Codex (xhigh)?

GPT-5.3 Codex (xhigh) is faster, producing output at 72 tok/s compared to Phi-3 Mini Instruct 3.8B's 0 tok/s.

Can Phi-3 Mini Instruct 3.8B process images?

No, Phi-3 Mini Instruct 3.8B does not support image input. Neither model supports image input.

Should I use Phi-3 Mini Instruct 3.8B or GPT-5.3 Codex (xhigh)?

It depends on your priorities. GPT-5.3 Codex (xhigh) scores higher on intelligence (54.0), but Phi-3 Mini Instruct 3.8B may be better for specific use cases like cost savings or speed-critical applications.

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View Phi-3 Mini Instruct 3.8Bdetails →View GPT-5.3 Codex (xhigh)details →Full pricing comparison →

Data last synced: March 26, 2026