Right now I wear a vest to jump because my dad makes me but I wanted to know others opinions on wearing a jumping vest or not.Also if you wear a vest to train do you wear it in a competition?
Your dad's making you wear a vest, because he wants you to have that extra level of protection. There's nothing wrong with that. The only time a vest is REQUIRED for jumping is if you are doing cross country. Otherwise, you may choose to wear a vest into the show arena (under your jacket, if jackets are required, otherwise just over your shirt as normal), but it is not required. You would not be penalized for wearing one.
If it makes you safer and your dad happier... why not? I don't personally wear one (I don't do cross country, not that that really matters) but I'm all for people wearing them if they want.
Goes the old adage, better safe than sorry. I wear a vest when I jump. It's safer, especially on my greenies, and provides an extra precaution for that "in case" factor.