Threading is soon to be come a thing of the past. Pipe is cheap ****, threaders are expensive and the lesser ones are fussy, and fittings are ****.
CSST is very easy to install and proven technology. The other advantage, like with PEX, is that you can install it very easily into existing joists and not have them below to interfere with ceiling finishes.
If you have to work with black iron pipe and can find a place to borrow a press tool, that's how I'd install black iron pipe these days. Just like PEX, just clean the pipe, put the fitting over it and press it on. Unfortunately even the Milwaukee 2773 is $3100... though they ARE running a rebate for the 1/2-3/4"-1" black iron pipe jaws for free. The Viega MegaPressG fittings are pricey but you'll be installing them in no time and with much more confidence in your finished product than messing with crappy threads and crappy Chinese fittings.