I spent a ton of time researching this a few months back as well and in the end I went with the Omega 8005, although the 8003 is equally good. Compared to the greenstar the price was far better, it has a much shorter clean-up time as my friend owns a greenstar and it easily took him 2-3 times longer to clean + assemble/Disassemble everything. Lastly I personally like how the Omega juices compared to the greenstar, particularly for fruits, which I found the greenstar lacked in by comparison.
If you can afford it I would definitely go with the Omega 8006 for the stronger auger, otherwise look on Ebay or buy the 8003 online. For the price I don't think anything can beat it.