I don't own a 380, and cannot make a good argument in favor of one. That said, they ARE wildly popular. So are Glocks. Hard to envision a Glock 380 not selling well, despite overall size being larger than some others.

As far as size goes, I've only shot a few 380s along the way, and my favorite by a huge margin was the 'large' Beretta 84, second was the Sig P230.

I'm not really a fan of tiny pistols though. Since I carry in a holster anyway, I just go straight to the Glock 17.