Essentially, at the scale I am looking at here, when I refer to a v-grind you can easily extend the concept to the scandi grind as well.
For a given knife blade thickness, the following diagram demonstrates the main difference between a convex grind (whether full or partial) and a v-grind.
If you pay any attention to the knife world, you have probably heard before that convex grinds are known for their toughness. The diagram above explains why that is.
Now, there are a lot of variables that can come into play when comparing two seemingly similar knives (although they are not). Those variables could be steel properties, blade thickness, grind angles, etc. Steel properties aside, what my diagram is trying to show the difference between the two grinds, for the same blade thickness.
The actual edge is the portion doing the work. But, it is backed up by the material behind it. If it is thin and narrow, there is a high likelihood of some type of damage occurring……think of an exact-o blade. If there is more metal there, the chance of damage is lessened.
As you move from the knife edge, up towards the top of the page (the red line), look what is going on with the material thickness at that point (green lines and blue lines). Each incremental movement along the red line will result in more metal behind the edge on the convex grind. Pretty simple, eh?
Now hopefully you understand why every time you pick up a hard use tool, meant for impacts (such as an ax) that it has this type of grind on it. Also, in an ax, the curvature of the convex edge is what helps the tool take large chips out of wood, rathering than getting stuck and binding. But, axes are a whole different topic all together, and I may address that in the future. But, the point still is the same.
Which is better??? Well, that depends on your purpose, I guess. I know for overall use, I have my favorites. You can read all about that in my Favorite Grinds article.