I've completed the MIG level 1 course this year, and next year I'm either doing MIG 2 or TIG 1 - still undecided.
I was in the same boat and plumped for doing MIG2. Glad I did, it takes everything to umm, 'another level'. It definitely builds on level 1, with welding in the vertical position and your welds are tested. I personally would regard level 1 as introductory, and level 2 is when you start churning out really useful welds.