M4A1- Custom VS Silver VS Adv

I need opinions on these 3 versions of the guns. Is there much difference between them?

I have a silver, and used to have 30 day Adv. Really no difference between those two.

Now my dilemma is that i have enough coupons for m4a1-custom, but i heard it got "nerfed". I play well with the m4a1-silver, but i feel like i could play much better if i got a custom.

Opinions?

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