Elect to depreciate it over 27.5 years. Remember, when you sell the property you are required to recapture and pay taxes on that depreciation in the tax year you sell. Two things are possible in the year you sell.
1) Recaptured depreciation is added to your overall AGI. If that makes your AGI to high for other deductions, then you lose those deductions.
2) It is possible that recaptured depreciation could bump you into the next higher tax bracket. Weather it actually does or not just depends on the numbers.