VM will throttle your download speed once you hit 3GB/month (4Gb/mnt if you pay for wifi tethering). And while VM runs on Sprint I think they are owned by Sir Richard Bernson of England, yet it doesn't matter who onws it, just what network it works with.
While Virgin Mobile can and will reduce your download speed Boost Mobile doesn't.
Most contracts state personal use, meaning you turn your phone off, or at least not downloading, when you sleep, cook a meal, or take care of personal hygiene. Sprint and Verizon have both blocked wifi tethering apps on the Android Play store (i.e. FoxFi for example). Personal unlimited does not mean true unlimited, nor business use (i.e. 24x7 use).