Build a Prusa i3 Mendel. Much more secure framework will yield crisper prints. I had build the original threaded rod Mendels back in the day but it is real difficult to keep the structure from tweaking when printing at fast speeds. This would inevitably lead to some shifting and loss of resolution. We do not seem to get that with the Prusa frame? All the rest of the printer is pretty much standard reprap stuff. Just my .02 and observations, your actual mileage may vary ;-)