There's a reason that full-page ads are a bad thing for the entrepreneur. (Unless that entrepreneur is in the media or advertising businesses, profiting off selling those full page ads.)
While the exact size of your ad should be tested for maximized profit, it's almost always going to be in the best interests of those with a limited ad budget to use a partial page ad.
Let me explain a bit more about how newspaper and magazine ads actually work:
Say you are a dentist who moves into town. You need to let the local folks know that you exist, so you put in a big ad, a full page ad, saying:
DR. FULLPAGE D.D.S.
123 Main Street
10 percent off with this ad.
Now, there are a very many things that are wrong with this ad -- way too many to dissect within the scope of one article.
But for basics, here are some of the things you ought to be aware of that would make a difference in response. Here are a few:
1) No one looks for a dentist.
"Whaadoyamean?" you exclaim. Well, when you think about this, you'll realize that people want a cavity fixer, a wisdom-tooth puller, a brighter-smile maker, a false-teeth creator... and if that mental image means something known as "dentist," we'll then, so be it. But it's not what they went looking for!
So, our dentist here ought to spend double the money, putting in two ads; one with a "smiler whitener" hook to attract the (yellow teeth-ed, at least in their own mind) new clients, and a separate, ad for those with a toothless grin, who want to have teeth so they can look good in pictures at the upcoming wedding of the grandkid whose finally settling down... well some of the toothless anyway. Other folks might want dentures because they want to eat an apple again- and yet others want dentures so when they speak it doesn't sound like "dey ain't got no peep!"
Which means that even in the world of advertising false teeth itself, there are multiple drill-downs, each one of which targets a different audience- which would treat every other ad for a dentist that didn't talk to their angle and desire would be totally ignored!
That's a basic primer into what an ad itself must have to be most effective within the "hook" or ad headline which draws the potential prospect for whom it is relevant and matched to read it. (You then want to use the AIDA formula -- attention, interest, desire, action -- to move them from having intrigued them over through the motions as smoothly as possible to convert them into a satisfied client who sends referrals.)
But, separately from that, the size of an ad can have a major impact on response. And bigger is not automatically better.
If a quarter-page, small ad gets a response, you'd want to test it against a half page. The half page could bring in double the response, which might be more or less the same return to you -- or it can bring in 500 percent higher response.
Sometimes, the smaller the ad, the greater return! Think about this interesting tidbit: many wealthy folks read the New York Times classifieds, even though they would not spend the time reading the ads costing 20 times as much in the paper itself! And even though they aren't looking for a job, somehow they still like to see what's out there these days and what competitive advantages they can gain for their business and pulse of economy awareness from the browsing.
And then there's ad placement: top half or bottom half of page? Inside half, closer to the center, or outer half, closer to the outside of the magazine or newspaper?
All these things can and do make a major difference in response. Each and every angle of how an ad is made, to the finest nuance, can really change the game. A toll-free number vs. a local number vs. a non-local number. A Web address that ends in .com and one that ends in .org. (For a charity website, a .org domain might generate higher returns and response then a .com domain. But a business using a .info domain? Yuck!)
In an English-language publication, or any other left-to-right language, the right-facing page is a better position than the left-facing page. (In Hebrew and Arabic, for example, the reverse would be true, because the newspaper is started by what you might consider "the end" and move toward the "beginning" of the book.)
And why is the right-facing page better? Don't people read both sides of the newspaper they hold in their hands?
The answer lies in the old army marching chant "right-left-right!" The nature of the human being is that when you turn the page, you automatically glance at the right-facing page first. You then go to the left-facing page to read, and then go back to the right-facing page to read it ("for real") before you again move on to turn to the next two pages.
And since advertising is much about nuances, it's that extra glance that gives your ad twice the chance of being seen on right facing page then a left facing one, which, in turn, using much of the same reasoning, is why a full-page ad is a bad idea for most.
Because if you are a full-page ad (and across the page is another full page ad... the horror!) then if nothing on your ad page attracts the client within milliseconds, they turn the page again and you are done and over with, ready to be fish-wrapping paper, while if there are other ads on the page, or some article text, it gives the reader a reason to stop at that page, and then your ad has a higher visibility and ability to intrigue the customer, giving it several times the mental real estate and visibility than an ad costing thrice as much.
Did you know that certain (ahem) famous watch companies will put in the same ad in the USA and Europe -- one with the man wearing a wedding band and one without. You'd never be likely to pick up on it unless you had both opened at the same time....
Aren't we humans fascinating as to what makes us tick?