Expect the CMP to start destroying weapons instead of selling them, given the current administration, so get your Garand while you can, they are scarce and collectible. The SKS you can get anytime.
To "the current administration" they are one and the same, with either one's continued availability no more likely than the other. If the M1 is a 'Big Evil Rifle' to them, then so is the SKS.
Re: the CMP "destroying weapons instead of selling them" - this is based on what?
OP: to me this is akin to asking "I have $50,000 - should I buy a $50,000 Cadillac or a $25,000 Buick?" If you've got the money and are willing to spend it, spend it. There's nothing wrong with a Yugo SKS - it does what it was designed to do in the way it was designed to do it.