I have owned an HK45, and HK USPc .40, and a Sig P220, my Sig I will never give up. I sold the HKs, because personally I didn't like the trigger pull, and I just like the heavier weight and overall feel of the Sig more. As for reliability, I never had an issue with any of the guns, put all kinds of ammo through them and they just kept going. Both manufacturers are popular with military and LE agencies. It comes down to what you like the most in your hand, and carrying, and what shoots the best for you. You won't be disappointed with either gun as far as quality goes. Best of luck.
By the way, I vote for the Sig. Buy a few of the 10 round single stack magazines for spares, and keep the 8 round mag in the gun. Just my 2c