DeepSeek V3.1 Terminus vs Grok Code Fast 1

Across our 12-test suite the head-to-head is evenly split: DeepSeek wins 5 tests, Grok wins 5, and 2 tie. DeepSeek scores 5/5 on long_context (rank: tied for 1st of 55 with 36 others) vs Grok's 4/5 (rank 38 of 55) — meaning DeepSeek is superior when retrieving or reasoning over 30K+ token contexts. Structured_output is 5/5 for DeepSeek (tied for 1st of 54) vs 4/5 for Grok (rank 26) — expect more reliable JSON/schema compliance from DeepSeek in our testing. DeepSeek also wins strategic_analysis (5 vs 3, tied for 1st vs rank 36) and creative_problem_solving (4 vs 3, rank 9 vs 30), and multilingual (5 vs 4, tied for 1st vs rank 36). Grok wins tool_calling (4 vs 3; rank 18 vs 47) and agentic_planning (5 vs 4; tied for 1st vs rank 16) — these reflect better function selection, argument accuracy, sequencing, and goal decomposition in our tests. Grok also wins faithfulness (4 vs 3; rank 34 vs 52), classification (4 vs 3; tied for 1st vs rank 31), and safety_calibration (2 vs 1; rank 12 vs 32), indicating fewer hallucinations and better refusal/allow behavior in our runs. Constrained_rewriting and persona_consistency tie at 3 and 4 respectively. In practice: pick DeepSeek for long-document retrieval, schema-constrained outputs, multilingual tasks and nuanced reasoning; pick Grok for agentic coding, reliable function/tool calls, classification pipelines and slightly stronger safety/faithfulness in our testing.

DeepSeek V3.1 Terminus charges $0.21 input and $0.79 output per million tokens; Grok Code Fast 1 charges $0.20 input and $1.50 output per million tokens. Assuming a 1:1 split of input:output tokens, cost per 1M input+1M output = $1.00 for DeepSeek vs $1.70 for Grok. At 10M (1:1) that's $10.00 vs $17.00; at 100M it's $100.00 vs $170.00 — a $70/month gap at 100M. If you measure output-only, DeepSeek saves $0.71 per M output (0.79 vs 1.50). High-volume producers of output tokens and budget-conscious teams should care most: at 100M output tokens monthly the price difference exceeds $71. Lower-volume developers or teams that need Grok's agent/coding features may accept the higher cost for quality tradeoffs.

Choose DeepSeek V3.1 Terminus if you need: reliable long-context retrieval (5/5, tied for 1st), strict structured outputs (5/5, tied for 1st), strong strategic analysis (5/5), multilingual work, and a lower output price ($0.79/mTok). Choose Grok Code Fast 1 if you need: agentic coding and tool-calling (agentic_planning 5/5; tool_calling 4/5), higher faithfulness and classification (4/5), visible reasoning traces for developer steering, and you accept higher output costs ($1.50/mTok) for those capabilities.