Just added the sub compact 9mm last weekend.
I now have XDm's in 45 (4.5") and 9mm (compact), and the XD in 9mm SC. I plan on the SC being my primary CCW, while the 45 with light and laser is the primary home weapon.
I put maybe 200 rounds through the SC and was very pleasantly surprised at the accuracy. Of course zero feed or fire issues, and at 25 feet you could cover 20 rounds fired rather quickly with a dinner plate. Taking my time you could cover them with a saucer.
It did shoot a bit low, and if I was not careful would go left, but I was really impressed with how close the rounds grouped with such a small gun.
The low and left would get resolved I'm sure once I worked on the trigger. Both my XDm's have PRP triggers, the 45 done by a smith and the 9mm done with a drop in kit. The improved trigger pull and shorted take up made both guns complete tack drivers. At 20 feet I can black completely out of the target with a full magazine.
My LGS had a used but near new M&P sc with aftermarket fiber optic sights he was selling for $495, and I stood at the counter for 30 minutes or so trying to decide what to do. In the end I went with the XD because I am very familiar with the guns, their triggers are far better, and the gun is just a bit shorter. Glad I did.