The only difference between an SBR and Pistol is adding the stock. The SIG brace can accomplish the same, no stamp, no $200, no paper work. If the state required rifles to be transported cased unloaded, it's not. If the State allows under 26" pistols to be carried loaded concealed in the car, it can.
You can build an 80% pistol and there's no requirement for any language, or numbers on it, an SBR has to be engraved.
If all the requirements of a SBR are no bother, go for it, establish a trust, pay money, Do Not Go To Jail. If the pistol seems to be quite a bit less hassle, forget the trust, keep the money, cross state lines without paper permission, carry loaded, Do Not Go To Jail.
It might seem that I'm biased but full disclosure means knowing all the facts and making an informed decision. I did - for my circumstances, which means knowing my state laws, too.
Like dropping a 16" 6.8 upper on the completed pistol lower and using it in MO "pistol" season where an SBR can't. Just got to keep it under 26" is all.
Your mileage may vary.