Which company has the "better" model depends entirely on what you're looking to build, how much control you want over the end product, and whether you believe ARM or Intel is building better chips to get you there in the long term. It's worth mentioning, however, that both Intel and ARM have taken pages from each others' playbook. Intel has done some limited fab work for other companies and some custom design work for major companies like Facebook, Google, and Amazon.
Analysts often spin Intel's limited foundry work into stories about how the semiconductor giant will throw open the doors and fab for all-comers -- forgetting in the process that Intel views its process technology advantage as its primary advantage over companies like Qualcomm, Samsung, and AMD. There's no chance at all that Intel would simply become a design firm at this stage of the game -- but the company has made changes to its core business in the name of building more flexible products.
Intel's fabs are one of the company's core strengths
ARM has no plans to launch a foundry, but the changes to the company's designs in the past six years can scarcely be understated. The Cortex-A8, A9, and A15 all pushed the performance and performance per watt envelopes. The Cortex-A5 and A7 improved performance at the lower end of the market but focus more on ensuring low power consumption. ARM has fielded more specific implementations in the past few years than in the decade prior and the company isn't slowing down -- the Cortex-A12, A53, and A57 are all set to hit market within the next 18 months.
Meanwhile, ARM has deepened its alliance with the foundries themselves rather than relying on its partners to carry the day. Multiple announcements on the company's timeline highlight joint agreements with TSMC and GlobalFoundries to optimize products for particular processes. This was likely an essential development, given that pace of adoption for new nodes has slowed sharply while the advantages of adopting them have declined.
It's not clear whether ARM's design focus or Intel's superior manufacturing will lead to better outcomes for the mobile market, but neither company is rushing to copy the other. Instead, both are implementing next-generation capabilities in a way that plays to their respective strengths.