Kate Abnett writing for Business of Fashion:
Among fashion and lifestyle magazines, the growing consensus seems to be that bigger is better. […]
“Advertisers saw the eyeballs going towards digital and their budgets weren’t going up, so if they were going to follow [readers] to digital, the money had to come from somewhere,” said Beth Egan, associate professor of advertising at Syracuse University, on shrinking print spend. Bigger trims, she added, are also “an interesting way to add content without adding pages,” which can quickly increase the cost of printing and mailing a magazine.
This comment obviously ignores the cost of the larger paper itself and the added weight and therefore postage necessary to mail a magazine even if page count stays the same.
“More than ever, everyone wants to stand out,” said Stefano Tonchi, editor-in-chief of W magazine. “The future of print is in premium content with a collectible quality.” According to Tonchi, W’s oversized format “serves as a luxurious environment for our bold and immersive imagery.”
Standing out in a crowded field — even more crowded if you included digital content delivery sources — is the real benefit here. But you also need to have the content to support it.
Indeed, while many in publishing seem to believe that a larger trim size will help to attract readers and boost advertising, a number of titles have taken the opposite approach, scaling down their books.
In 2013, InStyle whittled down its trim size, decreasing its width by 3/8 inches to 8 inches by 10 7/8 inches (the same as Vogue). […] In contrast to the titles adopting the look of coffee table tomes, Foxman believes InStyle delivers convenience for readers on the go. Most women “are not all that interested in carrying around something oversize.”
If we're talking bigger to stand out, then 3/8 of an inch isn't going to make a difference one way or the other.
A magazine's trim size is an important topic but this article is missing the real world considerations. And the first consideration is your publication's content and audience which is what InStyle is really pointing out here. If you're publication is full of great, curated editorial content, then a "standard" magazine size is perfect for your readership. If you're selling a premium magazine with beautiful photography/design, then more space on the page would be a benefit. And the larger trim size will help you stand out, literally, on the newsstand rack.
There are other considerations though. Are those standard magazine newsstand racks going to fit your new size or are you going to be stocked elsewhere that gets fewer eyeballs? Are your advertisers already creating ads for this page size or will they have to, and are they willing to, create unique advertising just for you? Is your printer set up with presses and paper to efficiently produce this new trim size or are you going to pay for paper and capacity which is being wasted on press? And, are your readers going to appreciate the expanded page layouts or would they prefer something easier to carry around and archive?