Unless you've got some epic hills in your area, I say go with the double. I have some pretty decent hills where I live, and even though it would be nice to have some easier gearing, I've been able to manage with a standard double.

If you have double-specific shifters and a front derailleur, then you can always switch out the rear cassette for easier gearing or opt for a compact front crank with smaller chainrings. If you've got a triple-specific drivetrain, a conversion to double is much more costly.