You want knives that are not easily broken by repeated (repeated hundreds of times) misstrikes. You will notice that knives labeled as "throwing knives" at retail are most often free of any bolster, guard, handle scales, etc. That's because those things will be destroyed in the learning process.
The key to successfully throwing a knife lies in repetition with the same knife. Only a superb champion of the craft would be likely to "stick" a knife he has never practiced with. Along these lines, a balanced knife is easier to learn with; however, any knife can be thrown and stuck if you practice long enough with it.