Head-to-head
Gemini 3.1 Pro Preview vs Gemini 3.5 Flash
Compare Gemini 3.1 Pro Preview and Gemini 3.5 Flash on the metrics that decide an agent workload.
| Metric | Gemini 3.1 Pro Preview | Gemini 3.5 Flash |
|---|---|---|
| Provider | Google Gemini | Google Gemini |
| Input / 1M | $2.00 | $1.50 |
| Output / 1M | $12.00 | $9.00 |
| Cache read / 1M | $0.20 (−90%) | $0.15 (−90%) |
| Reuse-adj @55% | $3.76 | $2.82 |
| Context | 1M | 1M |
| Cache capture | 83% | 85% |
| Warm TTFT | 360ms (−56%) | 150ms (−61%) |
| Quality index | 94 | 94 |
Teal marks the better value in each row. Reuse-adjusted assumes 55% prefix reuse and a 25% output share.
Pick Gemini 3.1 Pro Preview when your stack already standardizes on it.
Pick Gemini 3.5 Flash when it is cheaper once prefix reuse is priced in, it answers faster on warm cache hits, it captures more of the available reuse.
Gemini 3.1 Pro Preview leads on quality while Gemini 3.5 Flash leads on reuse-adjusted cost. Send latency- and budget-sensitive volume to Gemini 3.5 Flash and reserve Gemini 3.1 Pro Preview for the hard requests. Zumik's aliases route between them automatically under policy.
Frequently asked
Gemini 3.1 Pro Preview vs Gemini 3.5 Flash, answered.
Is Gemini 3.1 Pro Preview or Gemini 3.5 Flash cheaper?
At 55% prefix reuse, Gemini 3.1 Pro Preview blends to about $3.76 per 1M tokens and Gemini 3.5 Flash to about $2.82. Gemini 3.5 Flash is cheaper on that basis.
Which has the larger context window?
Gemini 3.1 Pro Preview has the larger window: 1M vs 1M tokens.
Which captures more reuse?
Gemini 3.5 Flash shows higher measured cache capture (85% vs 83%) in the Zumik corpus.
Let an alias pick for you.
Route to whichever model wins under current policy automatically. Zumik resolves the alias to the best fit per request, so you never hard-code a loser.