I disagree, I would not choose one channel unless it has proven chance that it can scale.
I am in favor of having two channels that equally work because they tend to change very quickly nowadays - one month over the other how they show ROI and where the ROI is.
As a marketing leader and a business leader, you have to move into where the revenue is. Yes, you have long-term games, long-term objectives, and long-term channels that you know can bring returns.
However, I wouldn't focus just on one channel all the time because the law of shitty click-throughs says something different.