Both

Hi, I've recently interviewed with two awesome ad agencies, let's call them A and B. Both interviews processes went really well. Agency A sent me an offer yesterday. I verbally accepted but haven't signed or sent anything in writing yet. Today I have a final interview with agency B. They said it's down between me and another candidate, and this will be the deciding interview. I'm honestly happy with either job. I've thought a lot about the pros and cons of either agency. But my main question is: Should I bring up that I got this other offer during my interview today? And Do you think there are any benefits to doing so? Or should I just wait to see if they even decide to hire me to bring it up?