I bought a G20 2 months ago. I have shot around 200 rounds through it without a hiccup. I bought it for an OC gun as well as a hunting handgun. Problem I have is finding ammo for the dang thing without spending $1 a round for everyday shooting.
I personally think that you should carry the biggest thing your comfortable with. At times that might be the G20, others it might be a little hammerless 38. Totally dependent on situation and your comfort level. If your worried about over-penetration with the 10mm just get frangible rounds for defense.
Good luck with whatever you decide.