Purpose - The paper aims to discuss the business issues surrounding the choice between the end-to-end internet architecture, in particular peer-to-peer networks, versus managed telecommunications architectures, in particular IMS, for the migration towards a next-generation mobile system. Design/methodology/approach - The paper organises the arguments available in the literature and technical field along four critical business design dimensions, providing a balanced overview of both sides of the argument. Findings - The paper discriminates between weak and strong arguments on both sides, and introduces a number of recommendations towards actors that will implement IMS. Research limitations/implications - The arguments collected from the literature and industry are not exhaustive but selected on their relevancy for business repercussions. Originality/value - While most position papers on IMS or P2P are written from an opinionated perspective, this paper offers a trade-off view of both side's advantages and disadvantages. It reframes the dispute as a number of design trade-offs to be made on various levels.