there is no price difference between a 120 and a 160. you won't be able to use the full 160 but only 128gb after formatting. which still is about 20gb more than the 120gb model. go for an external 500gb instead if you want storage space.
i installed a fully loaded 200gb into my g3, it all seemed to work fine, could access all the files, which was weird. then i tried to add a small file and that didnt work. though