When people call others buddy, it sounds very condescending and like you are better than them, kind of like you are talking to a child. I would recommend avoiding buddy. Dude is a great one to use for friends, it shows that you are comfortable and casual around them.

Both terms are very familiar. I personally hate being called 'dude' or 'buddy' by anybody: my friends call me by my name, people who don't know me can ask my name and use that. If somebody can't be bothered to ask my name, they shouldn't call me 'buddy' or anything like it.

I prefer people to call me by my first name or to ask if they don't know. I hate buddy or dude or even"mate' which is more British, although being a Brit I am used to this an don't pay too much attention to being called "mate" by total strangers for a one off meeting. Until they know my name. "Mate" derives from the British naval tradition and may be why it is or was common in Australia?, but i am not sure.

It's not rude, but it's very casual. For example, you wouldn't call your university professor a "dude". It's the same as saying "man," "buddy," "bud," etc.

American's us Dude to call stoners, skaters, or surfers. Another meaning is Homie or friend. for more information: https://www.urbandictionary.com/define.php?term=dude