I actually owned a sandblasting business for many years and can tell you a little about it. For one, sandblasting is great at doing the heavy parts. Axle housings, frame, skid plates, etc etc. What it is NOT good at is large flat panels, such as our hoods, cowl areas and middle of the doors. There isn't enough ribbing or contours in those areas to prevent warping from the heat and pressure of a sandblaster. That is best done with soda.
Soda can take off surface rust, but is best used for paint removal. It will not remove bondo, or any corrosion heavier than light surface rust.
As a rule of thumb, use sandblasting on the parts that are impossible to screw up, and use soda for the stuff you don't want damaged like the body parts I mentioned earlier.
I have personally sandblasted entire cars, but you have to be OH SO careful doing it. In fact I would turn down a lot of jobs on cars from the 60's to present day because they're so flat. I would also turn down parts of cars and have them taken to a soda blaster. Cars from the 50's and prior are fairly safe because of the thicker steel and heavy contouring of the style back then.
Another alternative is pecan shells/plastic media etc. Those are kind of gimmicky and don't have much of benefit over soda/sand.
The best part of soda is you can literally wash it into your yard with a garden hose after you pick out the debris you blow off your project. It's completely biodegradable.
In way of sand, a #4 grit is what you'd want to use. NO heavier. It is commonly called sugar sand because it looks like sugar in appearance.
Why is sand considered hazardous while soda is not? It's because true sandblasting sand is mixed with Silica (the stuff in the little packets in new shoes that says do not eat). Silica is mixed in the sand to repel moisture and keep your sandblaster from clogging. That's why you should never use playground or sandbox sand. Aside from that, playground sand isn't filtered very well and will ruin a commercial sandblaster. Just don't do it. Silica is hazardous because it can cause silicosis, which is hardending of the lungs. It can also cause other respiratory issues. I always used a full helmet and cape with fresh air fed into it for all of my sandblasting, and years later when tested, I had no evidence of anything wrong with my lungs.
In all fairness, you would probably have to sandblast for years with no protection to get silicosis. If you're just blasting something out in your yard, you'll be fine. Just be concious of the direction of the wind, or setup a fan so it blows the fine particles away from you. In short, the sand itself isn't hazardous, the silica is. You can hit it with water when you're done and fill in low spots in your yard, or toss it in the trash. Most of the silica blows away when it comes out of the blaster.
If you have any questions just let me know and I'll try my best to answer them. Hope this helps a little bit.
-Chris