Model comparison
Grok 4.1 Fast vs Nemotron 3.5 Lightning
Grok 4.1 Fast is the stronger model overall, scoring 41.4 to 40.0 on the Noometry Index. Nemotron 3.5 Lightning costs 3.1× less per token, which makes it the better buy when Grok 4.1 Fast's lead doesn't matter for your workload.
Last verified . 18 shared benchmarks.
NVIDIASummary
- They share 18 benchmarks with published results for both. Grok 4.1 Fast scores higher in 5 categories and Nemotron 3.5 Lightning in 3 categories; 8 gaps are clear of the uncertainty.
- The widest gap is in reasoning, where Grok 4.1 Fast leads 43.4 to 26.8.
- Nemotron 3.5 Lightning is cheaper at $0.05 / $0.20 per million input/output tokens, against $0.20 / $0.50 for Grok 4.1 Fast.
- Nemotron 3.5 Lightning accepts more context: 262K tokens versus 128K.
- Nemotron 3.5 Lightning has downloadable open weights; the other is API-only.
Side by side
| Grok 4.1 Fast | Nemotron 3.5 Lightning | |
|---|---|---|
| Provider | xAI | NVIDIA |
| Noometry Index | 41.4 | 40.0 |
| Released | 2025-06-27 | 2026-08-11 |
| Weights | Proprietary | Open |
| Context window | 128K | 262K |
| Max output | 30K | 262K |
| Input $ / M tokens | $0.20 | $0.05 |
| Output $ / M tokens | $0.50 | $0.20 |
| Results tracked | 32 | 18 |
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Category by category
Coding Nemotron 3.5 Lightning leads
Grok 4.1 Fast: 34.1 (#245), Nemotron 3.5 Lightning: 40.4 (#141)
| Benchmark | Grok 4.1 Fast | Nemotron 3.5 Lightning |
|---|---|---|
| LMArena Coding | 1411 | 1375 |
| LMArena WebDev | 1242 | — |
| ALE-Bench | 394.93 | — |
Agentic & Tool Use Not comparable
Grok 4.1 Fast: 36.3 (#39), Nemotron 3.5 Lightning: —
| Benchmark | Grok 4.1 Fast | Nemotron 3.5 Lightning |
|---|---|---|
| Berkeley Function Calling Leaderboard | 69.6% | — |
| τ²-bench Banking | 13.1% | — |
| LMArena Search | 1171 | — |
| Vending-Bench 2 | 1,107 | — |
Reasoning Grok 4.1 Fast leads
Grok 4.1 Fast: 43.4 (#49), Nemotron 3.5 Lightning: 26.8 (#127)
| Benchmark | Grok 4.1 Fast | Nemotron 3.5 Lightning |
|---|---|---|
| LMArena Hard Prompts | 1407 | 1337 |
| SimpleBench | 56% | — |
| NYT Connections (extended) | 87.4% | — |
| DTBench | 87.7% | — |
| ForecastBench | 61 | — |
Math Nemotron 3.5 Lightning leads
Grok 4.1 Fast: 31.9 (#221), Nemotron 3.5 Lightning: 37.5 (#155)
| Benchmark | Grok 4.1 Fast | Nemotron 3.5 Lightning |
|---|---|---|
| LMArena Math | 1408 | 1359 |
| MathArena Final-Answer Competitions | 60.9% | — |
| ProofBench | 4% | — |
Knowledge Nemotron 3.5 Lightning leads
Grok 4.1 Fast: 33.1 (#207), Nemotron 3.5 Lightning: 37.5 (#154)
| Benchmark | Grok 4.1 Fast | Nemotron 3.5 Lightning |
|---|---|---|
| LMArena Expert | 1399 | 1356 |
| Vectara Hallucination Rate | 17.8% | — |
Multimodal Not comparable
Grok 4.1 Fast: 37.0 (#76), Nemotron 3.5 Lightning: —
| Benchmark | Grok 4.1 Fast | Nemotron 3.5 Lightning |
|---|---|---|
| LMArena Vision | 1201 | — |
Multilingual Grok 4.1 Fast leads
Grok 4.1 Fast: 51.0 (#114), Nemotron 3.5 Lightning: 44.0 (#180)
| Benchmark | Grok 4.1 Fast | Nemotron 3.5 Lightning |
|---|---|---|
| LMArena Non-English | 1391 | 1295 |
| LMArena Chinese | 1441 | 1359 |
| LMArena French | 1415 | 1366 |
| LMArena German | 1404 | 1282 |
| LMArena Japanese | 1349 | 1206 |
| LMArena Korean | 1361 | 1238 |
| LMArena Russian | 1387 | 1253 |
| LMArena Spanish | 1413 | 1345 |
Instruction Following Grok 4.1 Fast leads
Grok 4.1 Fast: 72.7 (#133), Nemotron 3.5 Lightning: 69.6 (#170)
| Benchmark | Grok 4.1 Fast | Nemotron 3.5 Lightning |
|---|---|---|
| LMArena Instruction Following | 1376 | 1318 |
Long Context Grok 4.1 Fast leads
Grok 4.1 Fast: 42.4 (#126), Nemotron 3.5 Lightning: 39.9 (#165)
| Benchmark | Grok 4.1 Fast | Nemotron 3.5 Lightning |
|---|---|---|
| LMArena Longer Query | 1390 | 1314 |
Writing & Preference Grok 4.1 Fast leads
Grok 4.1 Fast: 57.2 (#131), Nemotron 3.5 Lightning: 48.5 (#201)
| Benchmark | Grok 4.1 Fast | Nemotron 3.5 Lightning |
|---|---|---|
| LMArena Text | 1408 | 1327 |
| LMArena Creative Writing | 1394 | 1254 |
| EQ-Bench Creative Writing | 1327 | 1280 |
| LMArena Multi-Turn | 1389 | 1328 |
Frequently asked questions
Is Grok 4.1 Fast better than Nemotron 3.5 Lightning?
Grok 4.1 Fast is the stronger model overall, scoring 41.4 to 40.0 on the Noometry Index. Nemotron 3.5 Lightning costs 3.1× less per token, which makes it the better buy when Grok 4.1 Fast's lead doesn't matter for your workload.
Which is cheaper, Grok 4.1 Fast or Nemotron 3.5 Lightning?
Nemotron 3.5 Lightning is cheaper. It lists at $0.05 per million input tokens and $0.20 per million output tokens; Grok 4.1 Fast lists at $0.20 and $0.50.
Is Grok 4.1 Fast or Nemotron 3.5 Lightning better for coding?
Nemotron 3.5 Lightning scores higher on coding benchmarks: 40.4 versus 34.1 in the Noometry coding category.
Which has the bigger context window?
Nemotron 3.5 Lightning does, with 262K tokens against 128K.
How many benchmarks do Grok 4.1 Fast and Nemotron 3.5 Lightning share?
18 benchmarks have published results for both models. Grok 4.1 Fast has 32 scored results on Noometry and Nemotron 3.5 Lightning has 18.