Speed vs Brain: What matters?

I think the best way to imagine it is to imagine your total effectiveness as combination of the two attributes - you call them Speed and Brain. I think your total effectiveness is best modeled as Speed times Brain. Increasing either one is useful, but increasing only one is not as helpful as increasing both.

If you have a 10 for Brain but a 1 for Speed (IE you know exactly what your opponent is thinking, but you can barely use a mouse), your total score is 10. If you are as dumb as a pile of bricks (Brain 1) but have great mouse skills (Speed 10), you might also have a score of 10. but a guy with moderate brains and fingers might have a score of 5 times 5 or 25, which would beat both of the extremely lopsided guys.

Finally, note that if you watch a lot of vids and up your Brain score by 4 points to 9, you're a 9 times 5 or 45. If you instead watched some vids and practice some "Speed", you're now 7 times 7, or 49. In other words, try to balance out both strategy and execution.

The best answer you'll get is that both are very important. Higher APM opens up new strategic possibilities, as the ability to react and plan faster gives you new options. Similarly, the effectiveness of your strategy is inherently capped by your ability to execute it.

While certain playstyles may be more forgiving to a lower APM player, and certain strategies may require less reaction time at the expense of requiring better planning, at the end of the day, you're only as good a player as both skillsets combined.

I'm going to possibly be a little controversial and say that long term I would say that speed is going to be the limiting factor and more a measure of potential.

There are physical limits to have fast you can act (which is actually limited by how fast you can think, rather than how fast you can physically press buttons because if you're just mashing buttons you could easily get 300+ APM but it's meaningless)

Have a good strategy is equally important to have, but it's easier to learn, especially with replays, videos and sites like this. Just because you didn't make up the strategy doesn't mean that you can't copy it and do it better than the person that did invent it.