Not a tablet, but I recently bought a factory reconditioned ASUS Zenbook 305CA (8GB, M-5Y71 CPU) for a similar purpose. So far so good. It seemed to me to be at the bottom end of the premium ultrabook market and about half the price of a XPS 13, much cheaper than an X1. Also, Linux support is good.
Windows 10 memory management seems better than Windows 7. You might get away with 4GB for some things but my gut feeling is that 8 would be preferable. My Win 10 desktop is currently sitting at 7.3 GB with Visual Studio and a bunch of Chrome tabs open.