Effectiveness should be based on marketing goals and business objective. All channels are useful for different purpose. To have an effective marketing strategy, you need to be multi-channel. Since customers are present everywhere. Based on my experience this is how I can categorize channels into the funnel:
Customer Acquisition - Search and Social
Branding or Awareness - Display, Video, and Social
Search
Search Advertising commonly used for acquisition based campaigns. This is most common advertising method for lower funnel acquisition strategy. Search advertising helps in finding right customers looking for services or product using keywords. Google, Bing and Yahoo Gemini are the popular search advertising platforms.
Ex: Company A is offering plumbing services. Business can show ads for people who is typing "plumbers" in search engines. This helps business to show results on top of organic results. So A can reach customers by showcasing the services when customers are looking for it. Text Ads are the commonly used Ad formats in Search Network.
Display
According to Forbes, 90% of marketers and agencies now say online display ads are good for branding. Because customers see your logo, service offering in ads. Most of the display ads are of the upper funnel. Awareness based campaigns. This helps customers in remembering the brand in case they require any service. This advertising nowadays marketers are using for remarketing. People come to your website and added a product to cart but did not buy due to various reasons. You can retarget with the same product and show him more often.
Ex: You might have seen various ads from Amazon with products you visit. This type of advertising is called dynamic remarketing.
Video
According to Forbes, 70% of agencies say online video is an efficient brand-building alternative to television--and 20% are moving some TV dollars to online. This format of advertising can be used for explaining about a brand or product. Few products cannot reach customer through images or text ads. When introducing new product or service video ads are worth trying. As a marketer, you need to be present everywhere.
• 92% of B2B prospects consume online video
• 4 billion videos are viewed on YouTube every day
• About one-third of shoppers will purchase a product after seeing a video ad
Social
Advanced targeting options on Facebook, and Twitter like self-reported interest helps marketers to reach specific consumers. According to Statista, 1.7Bn active users are there on Facebook, brands can engage with them answer their queries and enhance their experience with the brand and develop a healthy relationship with customers.
Overall in Consumer Decision Journey
In Trigger; Display Ads is the most effective and acts as a stimulus. Interactive display ads increase consumer's purchase intent (Source: Adobe study). In Initial Consideration and Active Evaluation; Search is the most efficient. Since 88% of consumers research products and services before making a purchase. (Source: ZMOT macro study, Google). In Moment of Purchase; Display Ads again if we considered off-site re-marketing and consumer re-targeting. In Post-purchase Experience; Social combined with Video is the most effective because people tend to share their experience (especially Generation C).