CMG sonic is basicly similar to Arc in that they both uses (partially) regulated output. IMHO, Arc has a lot more coolness factor compared to the sonic, but that is just MY opinion. the Arc will runs of about 5 hrs (depending on your battery brand, of course, as your milleage may vary /ubbthreads/images/graemlins/grin.gif ) and will then fall out of regulation and start its moon mode. The moon mode will allow you to perform most basic survival task such as finding another AAA cell /ubbthreads/images/graemlins/grin.gif . But the X1 is different from the other two. It uses some kind of focusing lens that project a tight round beam, so it might not too useful for near and close up work but too dim for lighting distance objects. the only thing I like from X1 is the form factor; it is simply as cool as its brother, the X5.
My suggestion is for you to buy Arc AAA. It's price (right now) also one of the many reasons that you should go and get one of yours. But if you think that Arc AAA maybe too small for you (which i think would not), go get the bigger CMG Ultra. More runtime, same brightness, similar price but with a bigger body and accept 1AA instead of 1 AAA.
the choice is yours. /ubbthreads/images/graemlins/wink.gif