Marketing or Sales, if you had to pick one, which one would it be? Both are equally important to the success of a company. In fact, one could easily argue that every department is critical to a company's success.
Marketing is essential for attracting leads and building awareness, but another considerable role of marketing is research conducted to understand your buyers. Marketing should develop the strategies on how to sell your products/services so that sales can more efficiently move prospects through the sales funnel. Understanding your target market, why they buy, who they are, where to find them, etc. is more important now than ever before.
With all that being said, the strategy is useless without execution; that's where sales come in. The role of sales should be to quickly qualify or disqualify leads and move them from the awareness stage to closing. The sales department is responsible for generating revenue, without which your company isn't going to last too long.
The most important take away is that companies need to stop thinking of it as "marketing or sales". They are not two separate departments, they are one, working towards the same goals. They need to have the same messaging, the same understanding of what is, and what is not, an ideal prospect/client. It is only when sales and marketing operate seamlessly that you will experience maximum success.