Grok 4.1 Fast vs Grok 4.20
For production agentic workflows and function orchestration, Grok 4.20 is the pick — it wins the decisive tool calling benchmark in our testing. Grok 4.1 Fast delivers equal scores on almost every other test while costing roughly 10x less, so pick it for high-volume, cost-sensitive apps that still need long context and structured output.
xai
Grok 4.1 Fast
Benchmark Scores
External Benchmarks
Pricing
Input
$0.200/MTok
Output
$0.500/MTok
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xai
Grok 4.20
Benchmark Scores
External Benchmarks
Pricing
Input
$2.00/MTok
Output
$6.00/MTok
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Benchmark Analysis
On our 12-test suite, the two models are nearly identical: they tie on 11 benchmarks and differ on one. Specific per-test results in our testing:
- tool calling: Grok 4.20 scores 5 vs Grok 4.1 Fast's 4 — Grok 4.20 wins. In rankings, Grok 4.20 is tied for 1st (with 16 others) out of 54; Grok 4.1 Fast ranks 18 of 54. This matters for function selection, argument accuracy and sequencing — Grok 4.20 is better for agentic tool orchestration in production.
- structured output: both score 5 and are tied for 1st (tied with 24 others). This means both are strong at JSON/schema adherence.
- faithfulness: both score 5 and are tied for 1st (tied with 32 others) — both stick to source material in our tests.
- strategic analysis: both score 5 and are tied for 1st — both handle nuanced tradeoff reasoning equally in our testing.
- long context: both score 5 and are tied for 1st (tied with 36 others) — both handle 30K+ token retrieval well in our tests.
- persona consistency, multilingual, classification, creative problem solving, constrained rewriting, agentic planning: all tied between the two models (scores equal and ranks similar). See payload for per-score values (e.g., persona consistency 5 for both, constrained rewriting 4 for both).
- safety calibration: both score 1 and rank 32 of 55 in our testing — a shared weakness on refusing/permitting edge-case requests. Implication: except for tool calling, you should expect functionally equivalent behaviour on structured output, long context, faithfulness, multilingual output and classification. Grok 4.20’s advantage is specifically in tool calling (score 5 vs 4) and its top rank there supports production orchestration use cases.
Pricing Analysis
Per the payload, Grok 4.1 Fast costs $0.20 per 1k input tokens and $0.50 per 1k output tokens; Grok 4.20 costs $2 per 1k input and $6 per 1k output. Example budgets (assume a 1:1 split of input:output tokens unless noted):
- 1M combined tokens (500k input + 500k output): Grok 4.1 Fast = $350 (500*$0.2 + 500*$0.5 = $100 + $250). Grok 4.20 = $4,000 (500*$2 + 500*$6 = $1,000 + $3,000).
- 10M combined tokens: Grok 4.1 Fast = $3,500; Grok 4.20 = $40,000.
- 100M combined tokens: Grok 4.1 Fast = $35,000; Grok 4.20 = $400,000. If you bill by output only, 1M output tokens cost $500 on Grok 4.1 Fast vs $6,000 on Grok 4.20. The cost gap matters for any high-volume deployment (SaaS, customer support pipelines, large-scale automation). Small teams or experiments can tolerate Grok 4.20’s premium for better tool orchestration; cost-sensitive production should prefer Grok 4.1 Fast.
Real-World Cost Comparison
Bottom Line
Choose Grok 4.1 Fast if: you need 2M tokens of context, top-tier structured output, long-context retrieval and faithfulness at the lowest cost — it costs $0.20 input / $0.50 output per 1k tokens and ties on 11 of 12 benchmarks. Choose Grok 4.20 if: you run agentic workflows or large-scale tool-calling where function selection and argument sequencing matter (Grok 4.20 scores 5 vs 4 on tool calling and ranks tied for 1st), and you can absorb roughly a 10x higher token bill ($2/$6 per 1k tokens).
How We Test
We test every model against our 12-benchmark suite covering tool calling, agentic planning, creative problem solving, safety calibration, and more. Each test is scored 1–5 by an LLM judge. Read our full methodology.