docs: note computer controls screenshots are faster for webgl

Add guidance that computer controls captureScreenshot is faster than
CDP Page.captureScreenshot for animation-heavy and WebGL pages, and
clarify GPU acceleration's scope: it speeds up page rendering, not
CDP screenshot capture.

Author: masnwilliams

browsers/computer-controls.mdx

@@ -158,6 +158,10 @@ kernel browsers computer move-mouse <session id> --x 500 --y 300 --smooth=false
 
 Capture a full-screen PNG or a specific region.
 
+<Tip>
+For WebGL and other animation-heavy pages, `captureScreenshot` is noticeably faster than CDP's `Page.captureScreenshot`. If you're driving a computer-use loop off screenshots, prefer computer controls. [GPU acceleration](/browsers/gpu-acceleration) gives an additional small speedup for computer controls screenshots, but does not speed up CDP screenshots.
+</Tip>
+
 <CodeGroup>
 ```typescript Typescript/Javascript
 import fs from 'fs';

browsers/gpu-acceleration.mdx

@@ -44,6 +44,10 @@ GPU acceleration is useful for:
 - Video processing and playback
 - Canvas-heavy applications
 
+<Note>
+GPU acceleration speeds up page rendering, not screenshot capture. CDP's `Page.captureScreenshot` latency is unaffected by GPU. [Computer controls screenshots](/browsers/computer-controls#take-screenshots) see a small speedup with GPU enabled.
+</Note>
+
 ## Availability
 
 GPU acceleration is available on [Start-Up and Enterprise plans](https://kernel.sh/pricing). Due to limited capacity during the research preview, GPU-enabled browsers may not always be available.