Cheaper. Yellow page advertising can cost thousands of dollars per month. With online advertising through Bing or Google, you can yield more results with $600/month. The cost of printing and distributing direct mail can outweigh the benefits of a response.
Faster. You don’t have to wait for printing or for an issue to be released. You can instantly publish, revise, and pause your online marketing at will.
Measurable. Offline marketing can be measured as robustly as online marketing. For example, programs like Mouseflow and Lucky Orange allow you to actually summarize every mouse movement on every page of your website. Google Analytics allows you track countless metrics including where your visitors came from, what pages they visited, the order in which they visited pages, and the number of responses (sales leads) you got from which page. Unbounce Pages and Google Optimizer allow you to test 2 advertisements against each other to determine which one performed better. Ion Interactive allows you do complex “multivariate” testing.
Changeable. You cannot change a book, advertisement, or piece of paper once it’s been printed. Online marketing can be quickly changed when you find errors or simply want to make a switch.
Customizable. You can decide what visitors see what through segmentation. This is more difficult to do with offline marketing because you’d have to mail out an entire catalogue of information.
Easier to target niche markets. There are plenty of niche magazines out there, but there are far more niche blogs. You can hand-pick which sites you want to advertise on.
Involves fewer people (and hence, fewer problems). With offline marketing, you generally require different people for printing, distribution, and marketing strategy/design. With offline marketing, there is no distribution or printing.
Looks better. Design usually looks much better on screen than it does in print.
More creativity options. Online marketing can involve animations and interactive elements that engage users. Users can segment themselves and participate in the marketing.
Easier testing/prototyping. It’s far easier to conduct experiments with prototypes using online promotion than with physical distribution.
Printing quality assurance isn’t necessary.
Pay-for-performance rather than for placement.
Automated. For example, you can make it so visitors to your site continue to see ads for your product/service as they browse the Internet. You can also set a budget per day and have an Adwords campaign run itself.