Alvin,
I have taken Green Vibrance, and I found it to be a good supplement for purposes of getting more greens. I have also taken just about every other superfood out there. All I can tell you, is that the one I am taking now is VITAFORCE, and you should probably at least check it out before deciding to take others. I started taking this one a few months ago, and am not going back to any of the other ones because this one is so much better.....
Check it out if you wish --http://www.organichealthandbeauty.com/VITAFORCE_p_140-81.html
There are numerous links on this page, but I think the most telling one is this chart where they compare the nutrient levels in VITAFORCE versus many of the other top selling green powders:
Nutritional Comparison Chart
Best,
Joey