Unlike the Texas Rig, the Free Rig falls squarely into the 'Freedom of Movement' bait category. All that means is that the rigging allows the actual lure significantly more play or freedom to move when rigged when compared to traditional bottom contact baits like a Texas Rig, or Football Jig. So, the Free Rig is to the Texas Rig as the Football Jig is to the Wobble Head. Besides the Free Rig, and Wobble head, the other main freedom of movement bait is the Carolina Rig.
On a Free Rig It depends on the bait you use as to how much different it will be vs. a Texas Rig. On baits like a Zoom Lizard or Ol Monster, the action isn't near as dramatic as when you use large surface area or floating/elastomer type baits.
For example, a Texas Rigged elastomer Bellow's Gill doesn't create much separation between the weight and bait when it hits the bottom, but on a Free Rig that same bait will create significantly more separation, which creates a slow spiraling fall after the weight reaches bottom.
A Free Rig is often referred to as a mini C-Rig. Both rigs enable the bait to be unimpeded by the weight, hints the freedom of movement term.
I fish Free Rigs mainly in heavy cover like laydowns, and brushpiles, not so much grass outside of weed lines so I can't really comment how it differs from a Texas Rig is submerged grasses. I can say that the Free Rig comes through heavy cover as good as the Texas Rig though.
Lastly, if you look at water tank Free Rig videos, the differences to the naked eye many times are hardly noticeable depending on the bait, however in practice and when you're not just dropping a few feet of line straight down into an aquarium, the effects are greatly magnified. If you allow the Free Rig to hit bottom on slack line, the separation between weight and bait is significantly increased. Just keep that in mind when you watch those tank tests.
Bottom line, you owe it to yourself to at least try a Free Rig out.