I have used them in my 55 before and currently have both. I am middle of the road, neither like or dislike. If you ask most shrimpers it depends on what you are going to be keeping. For Cardinas like CRS, and Tigers They recomend Aquasoil because it buffers the PH down, for Neos Like Cherries, the Eco is fine as is. Just be aware in the begining you will see your PH increase a bit for a few months till the tank settles in.
This is what i have been reading. And i do want to keep the Neos and Cardinas so i want to find one that will equally balance for both.