Which of the two ads below do you think performed better? Both used the same title text and URL (which is why the URL is not included in the images below). The body copy is the only difference between the two ads.
Look closely and you'll notice the ads are quite similar. They include the same basic ideas, the same numbers. They both include an exclamation point at the end of the second line of body copy. And yet, despite their similarities, one of these ads increased CTR by 111%. Can you guess which one?
Because of the similarities, it's harder than normal to guess the correct winner. It's unusual to see such a big difference between two ads that are so similar.
Alright, enough suspense. In this particular contest, the new winner is ad number one. The winning ad was written by "Vigor," and, as mentioned above, it increased CTR by 111%.
So why did the new ad generate twice as many clicks as the original ad? Let's take a look at the subtle-but-significant differences...
1. The losing ad uses a run-on sentence. There is no punctuation between the first and second line of copy, even though each line is its own sentence. This hurts readability. Not only that, the word "Available" is a wasted word. It contributes no additional meaning and should be deleted or replaced.
2. The new ad uses a single sentence that takes up both lines of body copy. This sentence flows better and may be a factor in why it increased CTR.
3. Rather than lead with a number, the winning ad leads with a powerful imperative verb: "Discover." The command to discover triggers the imagination and taps into the emotion of taking a bike tour of Europe. After all, isn't a European bike tour primarily about discovery?
4. The losing ad uses a strong call to action, but it promotes "Great Deals!" -- which is not necessarily the right thing to focus on. A few searchers may be looking for this, but most are probably searching for "European bike tours." So the emphasis on "deals" instantly makes the searcher think of the cost, which may not have entered his mind at this point. The winning ad takes a different approach...
5. Rather than emphasize "Great Deals," the winning ad promotes the routes themselves. Look closely at the wording. It basically says, "Discover Routes Today!" Of course, it includes how many routes and specifies the location as well.
6. The winning ad manages to squeeze the keyword "European" into the body copy. This increases visibility since this word will be bolded for most searches.
The bottom line: The new ad wins because it is more cohesive; it activates the imagination; it repeats a primary keyword; and it promotes one thing -- a variety of European bike routes -- instead of promoting "great deals," which is a bit premature (unless the searcher is specifically searching for deals).
I like this contest because it proves that subtle changes in ad copy can make a BIG difference in CTR. What's your takeaway?
By the way...
The BoostCTR writers have collectively spent thousands of hours improving pay-per-click ads on both Google and Facebook. It's what they do. Go ahead and put 'em to work... risk-free for 30 days! 
 About the Author: Ryan Healy is a direct response copywriter and BoostCTR writer. Since 2002, he has worked with scores of clients, including Alex Mandossian, Terry Dean, and Pulte Homes. He writes a popular blog about copywriting, advertising, and business growth .