I used the blocks before. While they work perfectly fine mine deteriorated overtime and left a hunch of sand like crap the sump. I won't use them again. I prefer to just put trays of rubble in. This is what I just put in my new build.
Most media is just a supplemental biological addition above and beond the rock in your tank.
For nitrate reduction I use an over size skimmer to remove doc before it breaks down.
I had a remote fuge with a 3+ inch deep sand bed that kept nitrate at close to zero.
For bio media in my new frag system I will use eheim substrate pro becuase I have a bunch stored away. I also like the bio rings like
Siporax as I have used them in the past. The Siporax does not break down same as the eheim product.
Some of the other media does breakdown over time especially if its moved around or handled alot.
I have never used the bricks or similar media but many have had it dislove and create a mess in the sump. Some people have used it with great success though.
Live rock rubble works but takes up alot of space and creates sand over time.