Tell that to my right foot and that was with years of experience of using 9".I never understand why people find 9" grinders so scary, I think they are as safe, if not more so than 4.5".
As for weight, 99% of the time you can have the weight sitting on the material and you are just moving the grinder along. You will also cut at least 20x faster with a 9" grinder.
As @Barking Mat states, one did put me in A&E.