To kick this off, I have to say that overall in my opinion CM is superior to TGMC. It's a more balanced, more serious version of the 2.
With that said, TGMC have some things that CM could implement. One of them is their weapons. First time I played I was kind of shocked that not only you can get an auto shotgun or a nade launcher as a regular marine, but you could even take an automatic 6-shotter nade launcher or an PRG right off the shelf. Or both as they cost 0 points. Want 20 claymores and 100 nades? No problem, it's all in your vendor. The amount of weapons - even extremely powerful ones - available for marines are amazing. I stopped playing PFC as a marine as a the same 4 weapon is boring, but TGMB has 20-30, maybe more?
Also engi is really satisfying, take 4-5 sentries, maybe a special sentry why not. It's really cool to set up a little outpost all by yourself.
But the place where TGMC shines over CM is the actual fight. Fight are...satisfying. Unlike in CM regular weapons DO damage to xenos. You can easily kill a small xeno in seconds with your barebone-base-no attachment rifle...and it's amazing. In CM you can shoot them till nighfall they won't take any meaningful damage, just go back and heal. But there I got more kills in a round than in CM in a week. And again, it feels amazing.
Also injured xenos LOOK INJURED. Why is this not a thing in CM?
With that said, CM is still an overall more refined game, but God damn the combat feels absolutely superior in TGMC. CAS, capet bombing, their version of OB and the sounds. Combat is sadly 10x better there than in CM. Can we expect any changes regarding this or we will only have the 4 guns with red blinking xenos forever?