"Just SBR it" means a $200 tax, trust set up fees, and it's permanently a rifle. Check you local laws - as a rifle it likely is not allowed to be carried or transported as a CCW pistol, and as an SBR you are required to have the ATF's written permission to transport across state lines.
And AR Pistol? No fees, much less hassle, no fees, exactly the same ballistic performance, no fees, and you could be able to use it in more hunting seasons than the rifle. Did I mention you don't have to pay any fees? It's still a 2MOA gun being shot at 18MOA targets where getting a hit is effective. Many SBR owners first went pistol and very few have documented or explained in detail just how much more the stock helped. None have expressed that it went from "barn door shooter" to "9 ring shooter" - because it doesn't. All it did was give them a Stamp to join a club supporting the worst anti gun ownership law passed in America - the 1934 NFA.
"Just SBR it" is not an guaranteed blanket expansion of your rights, consider your local laws and their impact.