Model comparison
Grok 4 Fast vs Phi 3 Medium 4k Instruct
Grok 4 Fast is the stronger model overall, scoring 39.4 to 33.0 on the Noometry Index.
Last verified . 17 shared benchmarks.
MicrosoftSummary
- They share 17 benchmarks with published results for both. Grok 4 Fast scores higher in 7 categories and Phi 3 Medium 4k Instruct in 1 category; 6 gaps are clear of the uncertainty.
- The widest gap is in long context, where Grok 4 Fast leads 63.2 to 34.0.
- Phi 3 Medium 4k Instruct has downloadable open weights; the other is API-only.
Side by side
| Grok 4 Fast | Phi 3 Medium 4k Instruct | |
|---|---|---|
| Provider | xAI | Microsoft |
| Noometry Index | 39.4 | 33.0 |
| Released | 2025-09-19 | — |
| Weights | Proprietary | Open |
| Context window | — | — |
| Max output | — | — |
| Input $ / M tokens | — | — |
| Output $ / M tokens | — | — |
| Results tracked | 30 | 17 |
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Category by category
Coding Too close to call
Grok 4 Fast: 32.5 (#271), Phi 3 Medium 4k Instruct: 32.9 (#268)
| Benchmark | Grok 4 Fast | Phi 3 Medium 4k Instruct |
|---|---|---|
| LMArena Coding | 1429 | 1130 |
| LMArena WebDev | 1159 | — |
| WeirdML | 42.9% | — |
Agentic & Tool Use Not comparable
Grok 4 Fast: 29.5 (#86), Phi 3 Medium 4k Instruct: —
| Benchmark | Grok 4 Fast | Phi 3 Medium 4k Instruct |
|---|---|---|
| τ²-bench Banking | 15.7% | — |
| Cybench | 30% | — |
| LMArena Search | 1171 | — |
Reasoning Too close to call
Grok 4 Fast: 22.2 (#201), Phi 3 Medium 4k Instruct: 21.7 (#214)
| Benchmark | Grok 4 Fast | Phi 3 Medium 4k Instruct |
|---|---|---|
| LMArena Hard Prompts | 1412 | 1127 |
| ARC-AGI-2 | 5.3% | — |
| Kagi LLM Benchmark | 66.1% | — |
| ARC-AGI-1 | 48.5% | — |
| DTBench | 82.7% | — |
| Epoch Capabilities Index | 144.2 | — |
| ForecastBench | 60.5 | — |
Math Grok 4 Fast leads
Grok 4 Fast: 38.9 (#123), Phi 3 Medium 4k Instruct: 33.4 (#202)
| Benchmark | Grok 4 Fast | Phi 3 Medium 4k Instruct |
|---|---|---|
| LMArena Math | 1419 | 1173 |
Knowledge Grok 4 Fast leads
Grok 4 Fast: 32.0 (#214), Phi 3 Medium 4k Instruct: 30.2 (#229)
| Benchmark | Grok 4 Fast | Phi 3 Medium 4k Instruct |
|---|---|---|
| LMArena Expert | 1411 | 1108 |
| Vectara Hallucination Rate | 19.7% | — |
Multilingual Grok 4 Fast leads
Grok 4 Fast: 51.3 (#111), Phi 3 Medium 4k Instruct: 30.6 (#263)
| Benchmark | Grok 4 Fast | Phi 3 Medium 4k Instruct |
|---|---|---|
| LMArena Non-English | 1396 | 1094 |
| LMArena Chinese | 1457 | 1108 |
| LMArena French | 1431 | 1110 |
| LMArena German | 1383 | 1101 |
| LMArena Japanese | 1352 | 1042 |
| LMArena Korean | 1357 | 954 |
| LMArena Russian | 1389 | 1145 |
| LMArena Spanish | 1415 | 1095 |
Instruction Following Grok 4 Fast leads
Grok 4 Fast: 73.2 (#121), Phi 3 Medium 4k Instruct: 57.6 (#268)
| Benchmark | Grok 4 Fast | Phi 3 Medium 4k Instruct |
|---|---|---|
| LMArena Instruction Following | 1387 | 1113 |
Long Context Grok 4 Fast leads
Grok 4 Fast: 63.2 (#3), Phi 3 Medium 4k Instruct: 34.0 (#255)
| Benchmark | Grok 4 Fast | Phi 3 Medium 4k Instruct |
|---|---|---|
| LMArena Longer Query | 1415 | 1120 |
| Fiction.LiveBench | 94.4% | — |
Writing & Preference Grok 4 Fast leads
Grok 4 Fast: 60.0 (#102), Phi 3 Medium 4k Instruct: 34.1 (#272)
| Benchmark | Grok 4 Fast | Phi 3 Medium 4k Instruct |
|---|---|---|
| LMArena Text | 1407 | 1138 |
| LMArena Creative Writing | 1387 | 1107 |
| LMArena Multi-Turn | 1414 | 1088 |
Frequently asked questions
Is Grok 4 Fast better than Phi 3 Medium 4k Instruct?
Grok 4 Fast is the stronger model overall, scoring 39.4 to 33.0 on the Noometry Index.
Is Grok 4 Fast or Phi 3 Medium 4k Instruct better for coding?
They score almost the same on coding (32.5 vs 32.9); test both on your own repository before choosing.
How many benchmarks do Grok 4 Fast and Phi 3 Medium 4k Instruct share?
17 benchmarks have published results for both models. Grok 4 Fast has 30 scored results on Noometry and Phi 3 Medium 4k Instruct has 17.