I can't imagine a situation where letting a program know about an acceptance to another program will improveimproves your chances of admission. To me, if I was on an admissions committee for school X and got word that you got accepted to school Y, all that would tell me is that you met a (largely unknown to me) set of criteria that school Y uses, which might share all, none, or some of the criteria that I use for admitting students to school X. By the same token, I don't think it will create too much antagonism.
On a personal note, I found that communicating with different schools AFTER I received a decision helped me. For example, I was accepted to programs both with or without funding. By letting the programs that initially didn't fund me initially know that I was accepted to a (rival) program with funding, I was able to turn one of my offers from non-funded to funded.
As others have said, once you know that you won't be attending a program, it is common courtesy to let that program know, particularly if you have an offer with funding.