And ARM has one huge advantage over Intel - everybody else except Intel has their own ARM SOC these days, so designers can shop around to get the chip they want, from the supplier they want. And they can easily switch to a different supplier without having to throw out their entire investment into the architecture.
Not really. The ARM part is pretty similar currently between all of them. With the exception of Marvell's line, they're all either stock ARM designs or slight tweaks (e.g. the improved floating point pipeline on Qualcomm's offerings). If one SoC vendor offers something better than another, it will typically be in terms of other cores on the SoC, and these are generally not compatible between vendors.
This is something that ARM is trying to fix with ARMv8. They intentionally delayed the release of the ARM-designed cores to allow a few other companies to have independent implementations arrive on the market at about the same time. This means that integrators will be able to shop around for ARMv8 cores that match their exact requirements.