I chose the ARM, but I'm now kind of wishing I had gone the 30-year fixed route.

There's another factor you didn't provide, which is very important. How much can the rate adjust every year in the 10th year? My logic was that with the cap on the adjustment in rates, I was also protected a bit.

The real risk that you hit a bad interest rate environment just as you're approaching that 10-year mark. It comes down to how risk averse you are. It's not just math...it's how much do you value certainty.