It has been revealed that the Switch gains a not insignificant performance boost when it's connected with the Switch dock. So naturally one would assume that games run better when the Switch is docked. Apparently that is not the whole truth of it all, as eurogamer's Digital Foundry discovered that, at least, Zelda BotW runs smoother in portable mode. According to them, Zelda - although having better texture quality in docked mode - suffers from minor stuttering if the Switch is docked. Basically they speculate that due the internal resolution gain from 720p to 900p when docked, issues with CPU clockspeeds and memory bandwith occur. Their explanation is reproduced below:
In terms of performance, it's immediately clear to the naked eye that the docked Zelda stutters in places where the mobile experience does not - and to confirm this, we manually counted frames by eye based on our camera shots to ensure accuracy in producing the performance test below. It's really easy to isolate this issue as it occurs frequently in the open world, right from the beginning of the game. In some places, we see the smooth 30fps update while docked drop down to a momentary 20fps - confirming a basic double-buffer v-sync implementation.
What's curious is that the stutter is fleeting, effectively ruling out GPU rendering as the cause - as the on-screen content doesn't change. And that begs the question - if it's a CPU issue, why do we have these issues at all bearing in mind that we know that docked and undocked CPU clock-speeds are identical at 1020MHz? Well, one thing we have to bear in mind is that although there is a big jump in GPU clocks as we move from docked to mobile, there's not a great deal of difference in memory bandwidth between the two modes.
This is only a theory, but it does make sense based on the data available. Laying out the maths here, docking increases pixel count from 720p to 900p, a 56 per cent in resolution. However, memory bandwidth only rises by 20 per cent, from 1331MHz to 1600MHz. Bandwidth is shared between CPU and GPU, so the higher resolution in the home console mode may be sapping memory bandwidth away from the main processor cores, making us more prone to slowdown when the CPU is under load. Bandwidth concerns may also explain why resolution doesn't scale closer in line with the difference in clock-speeds (307.2MHz or 384MHz undocked, 768MHz docked). Suffice to say, if you're looking to play Breath of the Wild with minimal performance drops, running undocked is the way forward.
...playing while docked highlights one visual improvement: texture filtering still isn't great, but it's clearly improved over the handheld version, resolving more ground detail in particular further away from the player. Will you actually notice outside of eyeballing screenshots? It's highly unlikely. Miniaturising the action onto the 6.2-inch screen makes the difference virtually indistinguishable, and the improvement - such as it is - manifests as a 'band' of additional texture detail just ahead of the Link character.
While this all sounds rather minor, it still does leave a slightly bad taste of doubt in the mouth about the Switch's processing power.