Which do you shoot the best? That is really what matters. Both are accurate and dependable.
My personal favorite is a P226. I have owned one since 1989 and carried one in LE and shoot one in IDPA and IPSC competitions. I like the grip feel, balance, and trigger much better on the Sig over the HK. I do have the short trigger and feel it makes a big difference for someone like me with smaller hands.
However, for IDPA, if you get a Variant 1 USP, you could shoot the same gun for SSP and ESP. Just DA the 1st shot for SSP and carry cocked and locked for ESP. You save on gear, holsters, ammo etc. plus you get twice the practice with the same gun.
If you have access to one of each for some test shooting, try some standard drills with a timer. Compare the speed,accuracy, and consistancy of your groups. This will help with your decision.
They will both serve you well and long. You can't go wrong with either IMHO.