I’m looking to sell my condo and buy a house this spring/summer, and will be facing this question: Get a 30 year mortgage or a 15 year?

The challenge for me is that I would be able to cover the 30 year’s monthly payments through my income alone, while if I were to go the 15 year route, I would need to dip into savings each month to cover the balance. Here’s some math:

(numbers pulled off a random Zillow.com house listing for examples, but the price range is right where I’m looking)

House sells for $229,000.

20% down

30 yr @ 4.139% = $893 per month

15 yr @ 3.134% = $1282 per month

Taxes and other stuff will be equal regardless, I should think, so I’m leaving that out of the equation. I can do 20% down and still have plenty leftover in savings for a cushion without touching retirement funds. Let’s say 50K leftover, just to put out a number. For what it’s worth, I’m single, and 47, so a 15 year loan would be convenient in that it would be paid off right around the time I might be thinking of selling to move somewhere warmer for retirement.

So I would need to pull $389 a month out of savings to cover the difference between the 30 yr and 15 yr. Logic would seem to dictate that if my return on my investment account is over 3.134%, I’d come out ahead by doing so - leaving aside the fact I’d be paying the loan off 15 years ahead of time, etc. But I’ll be damned if I can figure out the math to back that up.

What sayest the Straight Dope?