I like the old logo, but it is right that the proposed has better visibility in small sizes.
Purple is ok. I would prefer green, but that has it's own problems, mostly more widely usage and not least for color deficiency people. Blue/purple is always visible.
@lennstar - I also like the old logo as a piece of artwork - it has some lovely detail in it and, as you can see from the Commemorative Coin proofs, it works nicely as a large physical coin design. I initially tried most everything I could to simplify or strip down the original, but this ultimately proved unfeasible.
Do you have a preference on colour outside of the ones shown? I'm more than happy to mock up extra variants - it's a ten second job :). Purple really does stand out, as does blue - green ties in nicely with the general Gridcoin image but, you're right, it's widely used and not great for individuals with colour deficiency.