An extra notification for both sides would cause an even more crowded chaos inside banks, which is pretty realistic, actual bank roberries are a chaos.
There's a chance that cop-side gets slightly assisted from the change mainly cause every official gang organizes and gathers members of almost every other gang to enhance the defense that will be provided at its bank robbery. So since the majority of the "experienced" criminals that are in gangs are already there, gang-less criminals and whole cop-side are notified. Now, regarding gangless criminals, some of them could end up being a good addition in defending the bank robbery, some others could potentially tank bullets that are shot towards cops, helping the cop-side in a way.Also I've experienced my self getting shot and killed while cracking safes by a newbie, I assume he wanted to see what that red marker in front of safes does and it was fine by me since there was a back up cracker at that time. Same though can happen with inexperienced trainees that could possibly interfere with squad's tactics on how to breach through the defense and stop the bank robbery.
Leaving aside the speculations of how it could affect any side, a newbie, no matter which side he decided to start with, should experience a bank robbery as soon as possible, it may catch his eye and make the server seem more interesting to him, giving him one more reason to stay online and explore the server more.