This is an interesting question , for me I don't really think that there's a particular direction that favours more either Buy or sell, but rather mainly depends on your strategy and the opportunity which the trader is seeing in the market at any given time. I have seen some traders did say that selling is more profitable than Buying. When I started new as a trader, I was rather a good buyer than a seller but now I'm good at finding opportunities on both directions even more on the selling side, so someone can be more profitable at selling position today and tomorrow become a more profitable trader at buying position, verse varsa. However, all falls back to being the direction that the trader finds more profitable to him/her.
Perhaps, buying alone can't give you the profit that we are looking for, we need to sell them to make it possible.
I don't know what makes that question because if we have to analyze carefully, buying and selling are the tools to generate profit. As we say people just hold but they never make any profit from it unless they sell them at a higher price.
And my answer to that question is, none of them as they have worked together in order to earn a profit.