both are great units, but there are some differences:
Afaik the mach2gt will cool a little bit lower than the Vapochill LS, but the Vapochill has a better mounting system and should be less expensive.
From what I've read the vapochill seems to run a bit louder aswell
I'm about to get a mach1 modded with a chilly1 evap...it will cool as well if, not better and chilly's evaps have a great mounting system, and can be used for 478/939 and gpu's.....with the mach2 gt you will have to buy mounting kits for each socket you use.
plus...and this is a big plus, chilly's units start at about 1/2 the price as the others.
And now there is someone making lcd controllers called "g-froster" which seem to blow away the controls provided for both the mach2gt and vapchill