I'm not an installer, but I do know the basics. I do know construction. I'd rather attach a dish to concrete block than brick. An individual brick or two can loosen and ruin an installation. With block, you can hit two of four screws into solid material, much more stable, IMHO. The other two will hold just fine. Also, consider that many block walls have the voids filled with cement. If the wall itself fails, you have much bigger problems than the dish!
On a ka/ku dish block wall mount, we are required to put 4 bolts (1 in each corner of the foot plate) and 2 bolts in each mono pole (support arm)
You can easily mount each foot plate bolt in a different brick, and with little to no effort can put the 2 bolts in ea monopole in different bricks.
In the very unlikely chance that one of those bricks works it way lose, it will not play havoc on the dish at all.
Also, you can pretty much tell if a brick wall is stable enough to hold the dish for the next several years. If not, you have no business doing this type of work.
On hollow cinder blocks, the material is very thin.
While yes, any installer worth his weight would try and mount as many lags in the solid part, a minimum of 2 of the 4 foot plate lags will be in the thin hollow part.
However, this will still most likely hold fine for years, it still make me a little nervous.
Done plenty of them, both brick and hollow cinder block.
They all hold fine, but I guarantee the brick will hold stronger for longer.
BTW, I am well aware that many cinder block walls are poured (usually every other block).
They do this because the block is weak and this makes the wall stronger (as hollow cinder blocks are fairly weak).
Unfortunately there is no way to tell if the blocks are poured or not or which ones are poured until you drill in them.