Bettas like still water so a bubbler or a filter that puts a lot motion in the water is can be stressful.

Many people like having an established tank/filter for their bettas so that they don't have to worry so much about amonia levels getting too high and causing illness. This is usually the best route for busy/lazy people who won't monitor their betta's water and keep up with the water changes which muct be done more often with a bowl.

I personally like the bowls, plus I have so many that having larger, esablished tanks are out of the question. I do have sponge filters in my bowls which help with amonia levels.

Honestly, they only need a heater if your house is very cold. Most people keep their homes warm enough for a betta. If your house is kept colder than average, you will need a small heater.