A single sided deadbolt is great because locking and unlocking your deadbolt is controlled by a simple thumb turn. There is no hassle of worrying about locating your keys every time you want to use your lock. We usually recommend this type of lock if you do not have any windows within arms length from your deadbolt.
A double sided deadbolt really shines when there is indeed a window arms length from your deadbolt. The reason double sided deadbolts are good in this situation is so a intruder cant just knock out your window and reach in and unlock your door. However it is important to keep a spare key somewhere close to the door incase an emergency strikes and you need to get out in a hurry without worrying about finding your keys.