I too have a cheap chinese printer (JG Aurora A3, discontinued), and it surprisingly does have an all-metal hot-end. However, many machines of its class have a PTFE containing hot-end that will degrade under prolonged high temperatures (such as those found when printing ABS and Nylon).
My printer suffers from the Z-axis wobble problem. (It has a high center of gravity, so when the head carriage gets above just a few inches from the build plate, the machine 'sways' a little bit. Imperceptible to the eye, but sufficient to cause misalignment in the print if printing at any sensible speed.) There are various
project files out there to correct for this, by increasing the footprint of the unit, and thus changing its ability to sway like that.
I just want to avoid others having such headaches with a budget printer purchase, so that's why I mentioned it. If your prospective purchase does not have such problems, great!
If your printer can reliably get to ~240F, then I highly recommend the
Kodak nylon filament. Just be aware that you have to keep they filament VERY dry, because the hydrogen bonds that comprise the polymer are very attractive to ambient moisture, and that moisture gets vaporized when heated to the print temperature, and it causes bubbles in the print, which impacts the print significantly. If you keep it dry though, the prints are amazing; smooth, glossy, and very very strong and flexible. (I would avoid ABS, it is bitchy to print, and the parts are not terribly strong. PLA has reasonable strength, and prints well, but melts/softens at pretty low temperatures.) The kodak nylon prints at a lower temperature than other brands (typically 250F+), and is thus easier on budget printers.