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DeepSeek V3.5 vs Gemini 2.5 Flash

Side-by-side pricing, capabilities, real-world cost across common scenarios, and our editorial pick.

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all prices in USD per 1M tokens
OVERALL WINNER

DeepSeek V3.5

DeepSeek · released 2025-12-01

Quality (AA Index)81
Input price$0.14
Output price$0.28
Context128K
Throughput95 tok/s
P50 latency1.5s
View full pricing

Gemini 2.5 Flash

Google · released 2025-09-01

Quality (AA Index)78
Input price$0.30
Output price$2.50
Context1M
Throughput320 tok/s
P50 latency0.3s
View full pricing
Try DeepSeek V3.5 on OpenRouterTry Gemini 2.5 Flash on OpenRouter

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Head-to-head specs

Green column = winner per metric
MetricDeepSeek V3.5Gemini 2.5 FlashVerdict
Input price
/1M tokens
$0.14$0.30DeepSeek V3.5 −53%
Output price
/1M tokens
$0.28$2.50DeepSeek V3.5 −89%
Context window
max input length
128K1MGemini 2.5 Flash +7.8×
AA Quality
AA Intelligence Index (0–100)
8178DeepSeek V3.5 +3pt
Arena Elo
LMArena human-pref Elo (800–2000)
——Tied
Throughput
tokens per second
95320Gemini 2.5 Flash +237%
P50 latency
first token
1.5s0.3sGemini 2.5 Flash −80%
Vision
multimodal
—
Function calling
tool use
Tied
Reasoning mode
chain-of-thought
—

Monthly cost across common scenarios

Default usage assumptions
ScenarioDeepSeek V3.5Gemini 2.5 Flash
customer support
1000K req · 600/180 tok
$134$630
chat with docs
300K req · 4000/300 tok
$193$585
code generation
500K req · 2000/500 tok
$210$925
voice assistant
600K req · 800/200 tok
$101$444
Our pick

For most workloads, choose DeepSeek V3.5.

  • 53% cheaper input price, which compounds at scale

Roughly GPT-4o-class quality at roughly 90% off. Tradeoff is region availability (Chinese provider) and slower output throughput than Western frontier tiers.

Choose Gemini 2.5 Flash instead if: The price-performance benchmark for vision tasks. Strong multimodal, weak on deep reasoning. Pair as a fast first hop ahead of a smarter fallback.

Read our deep analysis

Why pick? Use both with smart routing

Phase 2 · gateway with fallback chain

Set DeepSeek V3.5 as primary, Gemini 2.5 Flash as fallback. One key, one bill, automatic failover when DeepSeek V3.5 errors.

PHASE 2 PREVIEW · gateway not live yetThis endpoint does not exist yet. The gateway is in Phase 2 — what you see below is a design preview of the planned interface, not a live API. We will email subscribers when it launches.
Preview the planned API call
$ curl https://api.aipricly.com/v1/chat/completions \
  -H "Authorization: Bearer $AIPC_KEY" \
  -d '{
    "routing": {
      "primary": "deepseek/deepseek-v3-5",
      "fallback": ["google/gemini-2-5-flash"]
    },
    "messages": [{"role": "user", "content": "..."}]
  }'

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