Why use an interactive toy? For a couple reasons. One reason is it makes your dog work for its food. If your dog has some extra energy this can help. By using an interactive toy you are providing mental stimulation for your dog. Mental stimulation will drain your dog's battery. Mental stimulation like this with repetition will also make your dog a bit more intelligent. This is because we are making the dog use its brain to figure out how to get the good stuff. Another reason is it will help your dog slow down. They can only eat the kibble as quickly as it comes out, which is not all that fast.
Why use a bowl? Why not? It is easy. I really don't have a problem with using a bowl. Just keep your eye open for any signs of guarding. (This can happen with interactive toys too.) I also don't recommend it to always be full. (But that's another tip in itself.) If you are going to use a bowl, I recommend teaching your dog to how to patiently wait until you get the bowl all the way to the ground and is released before it eats. I will make a video on this in the very near future.
Why use the kibble for training? If you use the kibble for training you are talking about a lot of repetitions. This is a fantastic idea for teaching a new behavior. If you have that mentality, technically giving a dog a bowl full of food is wasting a lot of training opportunities.
What do I do? My dog V eats out of a bowl for breakfast. This is mostly because the only reason I am getting out of bed is to feed him so I can get right back in. The other two meals that he eats are out of interactive toys. I like it because it slows him down and also gives him something to do.