Personally ,I have never worn two ball bags before, so I am more comfortable with just one, and I do not like the look of two ball bags, I think it looks bad when running around and such. And at a high level a baseball, that is why they have ball boys! I do not mind asking for more baseballs. I personally like 4 in the bag in 1 on the rubber. But there isnt a right or wrong answer. whatever you want to do and what you are comfortable with. My college association said it looks very unprofessional to only use one but I've talked to some high level guys who think opposite personal preference.