JTAG has been patched since 2009, it's very unlikely you'll encounter a console that has a dash that low.
RGH is the thing you want, more specifically, RGH 3, It's a new JTAG-esque exploit in terms of soldering.
RGH 3 seems to work on all consoles (idk about Xenon and Winchester) and is fairly easy to pull off if you have some soldering skills.