Consultancy R3:GC interviewed 223 leading PR and event marketers in eight cities and found that the average relationship between clients and agencies in these sectors lasted 2.8 years.
This compares to an average 2.5 years concerning their advertising counterparts.
However, 48% of PR briefs are still distributed on a project-only standing, typically undermining performance.
"China's marketers are under pressure to deliver sales - and no-one is feeling that more than the PR and event agencies they work with," said Sabrina Lee, director of R3:GC China.
"Marketers need to put in place more strategic, long term partnerships to see the benefits of collaboration and talent."
When choosing among shops, 79.8% of respondents named the digital skill-set on offer as a primary consideration.
"With more than 450m netizens online, PR agencies are playing an important new role in social media and iWOM in China - and marketers recognize the need to find specialist third parties in this area," said Lee.
The quality of an agency's staff, suite of services, credibility with the media and experience in relevant fields were further essential characteristics monitored.
OgilvyPR, part of the global network owned by WPP Group, secured the highest scores in its category for awareness and perception.
Lee said: "OgilvyPR has benefitted not only from the 'halo' effect of the overall Ogilvy brand, but also from strong, consistent thought leadership, and a lot of investment in marketing their capabilities to clients and prospects.
"They have set a high standard for other agencies to aspire to" she added.
Elsewhere, ten local operators featured in the top twenty PR providers, including Blue Focus, a firm running offices in Beijing, Shanghai and Guangzhou.
Such a status was also afforded to Genedigi, founded in 1997 and boasting 200 employees across three sites, and Trends, which has previously been tapped by Coca-Cola, Adidas and China Mobile.
Spearhead, Pico, and Highteam enjoyed similar pre-eminence regarding events, and Chinese companies in both sectors were argued to have benefitted from cultivating media links.
"Local agencies have often had longer, more consistent management and built up stronger 'guanxi' with local media," said Lee.
"In the future, we're sure to see more alliances and acquisitions than ever before as global players look to consolidate their positions."
Data sourced from R3:GC; additional content by Warc staff