I think the two main contenders for payment apps are Wexin and Alipay (支付宝). Both are vastly more popular than QQ these days.
WeChat and its dominance in its early days to a number of factors. Primarily in its infancy this is: good advertising, uniqueness compared to QQ (think MySpace -> FB), solid interface and voice memos. Voice memos were a killer feature that is massively more popular than in England (my experience) and I assume most of the West. Later on payments were added which enables anyone to have a business (receive money for services) and huge convenience for shopping or sending money to friends.
Alipay at the moment is less focused on social media like WeChat and more on interlinking services (Cinema, Shopping, Mobile payments, Utilities, Lifestyle etc). Also there's a massive advertisement campaign driving its use; currently each 24 hours users can scan a red envelope (红包) QR code an receive credit on their balance. I've receive $4~5 dollars a day, with an average of $1. Thats a free breakfast for most people.