both bikes are homo, and being in tasmania, most likely related by birth as well...
If you cant tell which is a faster bike by dragging them side by side, perhaps you need to get off the internet, and actually step out into the sunlight and find out....
The XR will be a more solidly built, reliable and sturdy platform.
The AGB29 will possibly handle a bit better, and be quicker in a straight line owing to the fact it will rev harder, has a greater engine capacity, is of a higher modification standard, and as Cactus pointed out, in "stock" form, is designed with greater performance in mind than the XR.
Mind you, a gun on a crf50 will run rings around a squid on a "Pro"(giggle) X140..