might I add that i have been following many of the vivi nova
threads very closely, as well as having 2 i use regularly.
the 1.0 as stated above has the vent holes on the threaded post much like a carto or clearo would. the 2.0 has the vent holes on the actual bottom end cap that are visible even when screwed into your pv.
as far as performance they both work well for me, but im also running long wicks on both, never bought the 2.0 in a kit so, not sure how it would work with the short wicks. so i guess im using a 2.25 vivi nova since its a little of both the 2.0 and 2.5