Facing a similar problem, I ended up choosing a Lenovo Thinkpad T440s (fully loaded), which gives me lots of battery life, a 3G modem to connect from everywhere (supported out-of-the-box by Ubuntu), and a set of high-end desktops and servers to do the heavy lifting. I get best of both worlds: I can develop and test things on my (still pretty fast) laptop, and once I have basic tests passing I push my code and remote-run jobs on more powerful servers that I don't really need to carry around with me.
I noticed the same benefits using Xubuntu 14.04. A lightweight user interface, very fast and easy to use. The OS is also very fast to install, very fast to boot, everything just works and updating is smooth. It may not be as "fancy" as regular Ubuntu or Mint, but I find Xubuntu very stable and polished (our usage is file and compute servers/clusters, desktops, mostly software development and office work).
"They" know which SIM connects to which cell tower, so I don't understand how this phone prevents tracking. Did I miss something?