I would choose the new American Pistol as I own the SR45 and I am not a fan of that pistol. The American feels better and has a better trigger and better fit options, however that is MY opinion and you should decide which you prefer.
The RAP that has been released has no mag disconnect or manual safety, what Ruger is referring to as the Pro model, that may be a consideration as well, do you want a manual safety?
Good luck with your decision. If you decide to purchase the SR, I would wait as prices will begin to drop with the intro of the RAP....my guess.