Yes I have used many firearms in the corp, and also as a LEO, however I have never fired or handled a G30 or G36 which this thread is about, and that's why I am asking !!!
I have both the G36/30. I also have the G23 and 27.
G36: Single Stack 45 ACP, 6+1, Accurate and reliable.
Pros: Thinner and lighter, Fits a G23/27 IWB holster, Tuckable in an IWB holster
Cons: Lower capacity, no other magazines work with this
G30: Double Stack, 10+1, Most accurate, Reliable,
Pros: Less recoil (thicker grip), can accomodate the Glock 21 Magazines, Higher capacity
Cons: Heavier, Needs own holster (doesn't work with my 23/27/36 holster), thicker, only ideal for untucked shirt for me
To me, I feel more confident with the G30 regarding accuracy and capacity. I will occasionally carry a G21 magazine for a backup. I need to use a thick and heavy duty belt or it will weigh my pants down. I carry my thinner guns like the 23/27/36 during the warmer months.