Google Gemini 3.5 Flash vs Grok 4.5: Speed or Spend
My call: Google Gemini 3.5 Flash wins if raw response speed is the fight, but Grok 4.5 lands the cleaner cost punch for output-heavy workloads. Gemini’s measured 284.2 tokens per second is the headline number. Grok 4.5 counters with $2.00/1M input and $6.00/1M output pricing.
Speed: Gemini comes out swinging
This round is not subtle. The current benchmark material lists Google Gemini 3.5 Flash as the fastest measured model at 284.2 tokens per second. That’s the kind of number that matters for chatbots, coding assistants, customer support triage, and any workflow where users feel every delay.
Grok 4.5 doesn’t get a speed number in the provided benchmark set, so I’m not going to pretend it does. That absence matters. If your top KPI is latency, Gemini has the only hard speed stat on the card, and it’s a big one.
Price: Grok hits back on generated tokens
Here’s where the fight gets spicy. Google Gemini 3.5 Flash costs $1.50/1M input tokens and $9.00/1M output tokens. Grok 4.5 costs $2.00/1M input tokens and $6.00/1M output tokens.
So Gemini is cheaper when you’re mostly reading prompts, documents, and tool results. Grok is cheaper when the model talks back a lot. Using those prices, Grok becomes cheaper once output tokens exceed one-sixth of input tokens. For agents, report writers, and long-answer assistants, that’s not a rare scenario.
Benchmarks: don’t overread the leaderboard
The current landscape is tight: the top 15 models are separated by as little as 3 percentage points in benchmarks. That means neither side gets a crown just for vibes. The material also says Grok 4.5 is the lowest-cost option among top performers at $2.00 per million tokens, while Gemini 3.5 Flash owns the speed lane.