Gemini 3.8 Flash High vs Grok 4.6 Xhigh: which is faster?

If you only looked at the intelligence index, Gemini 3.8 Flash (High) and Grok 4.6 (Xhigh) would be hard to tell apart. The figures come from tracked catalogue data, not from our own testing, so treat them as a starting point for a trial on your tasks. Gemini 3.8 Flash High streams output at about 121 tokens per second, twice the rate of Grok 4.6 Xhigh.

Waiting time

Once a response is under way, Gemini 3.8 Flash High produces roughly 121 tokens per second against 62 tokens per second for Grok 4.6 Xhigh. Gemini 3.8 Flash High is ahead by 96% on throughput. Before any text appears, Gemini 3.8 Flash High takes 27 seconds and Grok 4.6 Xhigh 47 seconds. Grok 4.6 Xhigh waits 1.7 times as long before its first token. A first-token wait of that length suits background work better than live conversation.

Put together, an 800-token answer would take about 34 seconds from Gemini 3.8 Flash High and 60 seconds from Grok 4.6 Xhigh, counting the first-token wait.

When they came out

Gemini 3.8 Flash High arrived on September 2, 2026, 21 days after Grok 4.6 Xhigh (August 12, 2026). They are effectively contemporaries.

Overall capability: effectively tied

The intelligence index has them at 30.8 and 31.0, Gemini 3.8 Flash High first. A gap that small is inside the range where one aggregate cannot name a winner.

For context, that places Gemini 3.8 Flash High 50th and Grok 4.6 Xhigh 49th out of 109 scored models still on offer.

Specialist coding and math indexes are missing for both, so treat the overall score as the only capability signal here.

Running costs

Gemini 3.8 Flash High lists $0.75 per million input tokens and $3.75 per million output tokens; Grok 4.6 Xhigh lists $2.00 and $6.00. Grok 4.6 Xhigh costs 1.6 times as much per output token.

A reference job of 1 million input tokens and 200,000 output tokens costs $1.50 with Gemini 3.8 Flash High and $3.20 with Grok 4.6 Xhigh, so Gemini 3.8 Flash High saves $1.70. Scale it up to extracting fields from 20,000 pages of 1,500 tokens into 150-token records and the bill is $33.75 for Gemini 3.8 Flash High against $78.00 for Grok 4.6 Xhigh.

Score per dollar

A blunt value measure, blended price over intelligence score, puts Gemini 3.8 Flash High at $0.049 and Grok 4.6 Xhigh at $0.097 per point. With scores this close, Gemini 3.8 Flash High is simply the cheaper way to buy the same capability.