An omnichannel marketing strategy will involve both physical and digital channels (such as stores and websites). The goal of omnichannel marketing is to provide consumers with a convenient, seamless, and varied shopping experience that will allow them to fulfill their needs in numerous ways. With an omni-channel strategy companies create a seamless brand experience.
All these marketing actions that companies use to reach out to customers or prospects in order to engage with a product / service. This can be a flyer, an email, an online advertisement, a billboard, radio ads, etc.
Some of the benefits are that the company controls how the product / service is being communicated, which the niche audience is, create a very direct call to action, make optimizations through testing.
Online marketing uses all the latest technologies (social media, SEO, online ads, email marketing, etc), it is much more interactive and measurable. Classic / offline marketing is mostly based on printing material and the ROI takes more time to be measured, if ever actually measured. Online marketing is much more effective, and cheap, while giving much more space for experimentation and testing.
ROI on traditional marketing is much harder to measure than in online marketing. So to actually measure if the both create the same ROI, is not something easy to say. Most probably, online marketing is much more effective most of the time, since, if done correctly, can be very precise and so measurable that if it does not work marketers can make immediate adjustments.