IMHO the switch to the 9-mm was done purely to accommodate the LAY-DEEs and please DACWITS, not Military reality.
I also dislicke any shoulder fired or crew served weapon less that 7.62-mm or .308.
I don't have a big problem with our .223 rifle cartridge, especially with the SS109 bullet. But nevertheless I wish we had picked a rifle cartridge with just a bit more "heft" to it.
On my last tour in Iraq I met one guy who carried an M-14. I was envious. He wouldn't tell me how he got it.