Well, it's kinda off-topic, but...
On one hand, no such thing as too many guns, right. AR-15 is better in some regards (lighter, less recoil, more customizable), but Mini-14 is a very nice and reliable semi-auto, and the more traditional stock geometry is more comfortable for some shooters. And yeah, most models don't fall under the old AWB rules. For any future AWB laws, who knows. It does seem that the focus of the gun control crowd is shifting more toward all semi-autos, but no way to be sure.
Which brings me to the flip side of the coin. If a ban happens, you can buy a Mini-14 then - what's the point of trying to be ahead of that game? Further, if the AWB comes with a grandfathering clause, owning AR-15s before the ban may be beneficial than having a compliant firearm from the get go. And last but not least, an AWB that still allows Mini-14 will probably also allow you to just slap a fin grip on your AR-15 to make it compliant, without spending nearly as much. Folks in California do that all the time.
As for the advice about non-compliance from other folks... honestly, I understand the defiant attitude on 2A subreddits, but expected a bit better here. If your goal is to avoid trouble, stockpiling illegal stuff that can saddle you with a felony charge if it surfaces in any context (even if overzealous firefighters or EMTs spot it in your house, or if you get pulled over for speeding) is not a good plan. The probability of that kind of an event is far greater than the probability of a Soviet space zombie invasion that can only be repelled if we keep our flash hiders and pistol grips.