Eagerness to bust caps...
... can seem pretty widespread on the internet.
I'm not eager to bust caps. I prefer de-escalation where possible.
However, given a pair of bullies, already on my yard, and already closed to 10-15 feet while mouthing threats, I'm not so sure simply walking away would be advisable or even possible.
Having dealth with human bullies and aggressive dogs, I feel much safer facing them than turning my back on them, or even letting them think I'm turning my back on them.
With both human bullies and aggressive animals, it can be deadly to let them think you've turned tail.
This isn't about chest thumping, it's just observation from firsthand experience. I used to be one of those guys who felt one could reason with anybody, or walk away from anything.
There's more than one reason I got into wrestling in school, and martial arts as an adult. Some of those reasons have to do with bullies who didn't believe in letting people walk away.
Given your average pair of bullies, I think that even without a gun I might be an unpleasant surprise for them; I would still be very uncomfortable about turning my back.
This is why I'd tend toward verbally warning them, and trying to back them down with body language while letting them know the cops would be called out again.