Advertisers are flirting more with paid ad offerings from Facebook and Twitter, but it's a cautious courtship. Even as brands boost their social-media spend, only a relatively small portion of it is going to ads, according to a new survey of Ad Age readers.

In May, Ad Age and RBC Capital Markets jointly conducted their fifth major survey of marketer attitudes toward social media. The survey polled 1,682 executives at marketing, agency and media companies for their opinions on Facebook, Twitter and YouTube, which was included for the first time. The number of responses varied for each question.

Marketers reported spending slightly more in digital and social-media channels than prior surveys. But that spending continues to be a relatively small slice overall marketing budgets.

A little less than half of respondents -- 45% -- said they spend 1-10% of their overall marketing budgets on social media, while 38% said they spend more than 30% on social. In a survey of Ad Age readers published in September, only 29% of marketers said spending on social was more than 30%.

Advertisers largely see social-media advertising as a branding channel. Asked to rank their goals for social, 39% of respondents listed "building awareness and sentiment for my brand" as the top priority. "Driving traffic to my website" was a distant second, with 16% citing it as their top priority.

Around 84% of respondents reported using Facebook, making it the dominant social platform. In addition, Facebook commands a greater share of digital budgets than Twitter and YouTube.

In the fall, the influence of "organic reach" on Facebook started to decline dramatically, upsetting marketers who had spent time and effort building up fans on the social platform. To Facebook's benefit, it may have helped steer brands toward paid ads. In the most recent survey, 83% said they had paid for ads on Facebook, up from around 70% in the September poll.

But as marketers plan for the coming year, they appear to be looking more at Twitter.

Nearly half of respondents -- 44% -- said they had increased their spending on Twitter over the past 6 months and 63% said they planned to do so over the next year. By comparison, 59% said they expect to spend more on Facebook. And more marketers surveyed said they plan to decrease spending on Facebook (11%) than on Twitter (7%).

Marketers found both Facebook and Twitter offer more compelling mobile products than desktop.

Some 36% of respondents said the ROI on Facebook's mobile-ads was "much greater" or "somewhat greater" than its desktop offering; 26% felt desktop proved better. For Twitter, 44% claimed it offered better ROI on mobile than desktop. Very few respondents (8.6%) felt that returns on Twitter's desktop products were greater.

In the first quarter, Facebook netted 59% of its ad revenue on mobile, while Twitter's total was 80%.

Ad Age readers are increasingly experimenting with Twitter's ad products, too. Less than half of respondents polled in November said they spent any of their Twitter budget on ads. Now, around 73% of marketers reported using Twitter's ad products.

Promoted tweets are still the favored tool. The format was used by 79% of respondents, more than the other three offerings -- promoted trends, accounts or an "Amplify" TV deal -- combined.

Still, marketers spend relatively little on the products. More than half of respondents (65%) reported spending less than 10% or none of their Twitter budgets on paid ads. Their dollars mostly go to managing accounts, not Twitter's bottom line.

With "Amplify," which launched in May, 2013, Twitter is trying to promote its relevance as a supplementary "second screen" for TV marketers. Facebook is making a similar pitch, but advertisers aren't diving into either. Only 12% of respondents said they used Facebook and Twitter in conjunction with a TV campaign. And just 7% said they were considering doing so.

Google comes out as favored winner for ROI. Respondents ranked the search giant as the best ad platform for ROI, and its video channel, YouTube, fell fourth behind Facebook and Twitter.

Slightly more than half of respondents reported using YouTube as a marketing channel, although very few marketers allocated significant portions of their digital budgets to the platform: 30% of those using YouTube reported zero spending on its ads.

However, 54% of respondents said they expect their YouTube ad budget to increase over the coming year.

The full results of the survey are available to DataCenter subscribers.