Firstly, they do work, but it depends on what stations are nearby. Also, you mentioned cinder block walls, that is a huge obstacle, walls, trees, buildings, etc, which is why people that have these put there antennae up high, tower to attic.

Use this guide, type in your address/zip to see what channels you can pull in, walls aside, and see if it is worth it.

If lots available, I would try the type of antennae you linked, that is the sort I am using now. When I lived in an area with lots of stations, I used this one, which is more costly and larger, and it is great, but don’t spend the extra money if walls or lack of stations are going to be your downfall, it won’t matter.