I received an offer for new position from company A (senior engineering position), and tried to negotiate a for slightly higher salary. They accepted and gave me 4 days additional to submit final decision in writing.
Two days later, I am getting a second offer from company B (also a senior position) with which I also interview around the same time. They offering slightly larger salary than what I tried to negotiate with company A and longer vacation package.
I kind of prefer company A, but don't want to turn down a better offer from company B. Can I negotiate salary or vacation a second time with company A? Is it ethical or would I better just go with what I was able to negotiate the first time?