The Legend of Zelda: Breath of the Wild is out on Nintendo Switch and Wii U today. As noted in the Shacknews review, it has some slight but surprising performance issues in docked mode on the Switch. Now we have some actual data to go by, thanks to a side-by-side comparison.
Digital Foundry put Breath of the Wild through its paces in the video below. It covers a wide range of technical specs including its resolution, draw distance, and some of the effects that bring Hyrule to life. Around the seven minute mark, DF starts examining the framerate, reaching the same conclusion our own Jason Faulkner did: while the portable mode runs smoothly, the docked mode mysteriously dips.
In their testing, it ran at a solid 30 FPS in testing on the portable mode, and would usually run at 30 FPS in the docked mode as well. However, it could take a dive, going as low as 20 FPS. They note that near the beginning of the game, when heading down a mountaintop with foliage, and engaging in battle with your first enemy, is a good spot to see it for yourself.
What's odd, according to their tests, is that this doesn't necessarily occur when there's a lot of action on screen. Sometimes the dips seemed random, which made them hard to predict and unexpected. The Digital Foundry also notes this is with the day-one patch installed.