...Wow. Anyway, Jtags are wonderful and the options regarding what you can do with them are endless. That being said, for the average joe i would not Recommend a jtag. You need to have a passion for modding in order to go beyond mw2 lobbies. If you just wanted one to host lobbies with that would be a large waste of money, as it would get old quick. Ask anybody who previously owned a jtag, they probably hosted a few Mw2 lobbies and quickly got over it. If you are like me however, and you love coding and creating new patches and working with different ideas/concepts then a jtag/XDK/RGH would be perfect for you. If you don't know how to code but you would like to learn then that's fine too! everyone starts somewhere, learn C#/C++ and watch some tutorials on youtube regarding how to make basic infection patches (thats what i did) It will help you get a feel for what you're doing, then once a bit more experienced move on to editing menu's..until you can create one from another menu base. As far as which one to get, it all depends on what you're willing to spend and how dedicated you are. If you were all out dedicated then go for a XDK (devkit) but im going to assume you're not so in that case buy a RGH. They are reliable, and they can do everything a jtag can do.
Best of luck with your Jtag journey!