I'd recommend having both fixed.

I think medically it's "easier" to have a male neutered since it's a simple snip, while a spay is a little more intrusive. However, if you only fix the male, you'll still have the problem of unwanted puppies should a intact male come roaming while your female is in heat. (dogs can climb fences)

And there are the risks of ovarian cancer in non-spayed females.

My female was spayed at 3 years by the Humane Society and she bounced back pretty quick. Though they suggest little to no strenuous activity.