What benefits does a sniper rifle offer over a rifle?

Sniper rifle has slightly higher damage which is barely noticable. It also has better accuracy then rifle, and longer range. Which means sniper rifle will miss less often when shooting at enemies that are far away, but as you noticed yourself it will miss more often in close range when compared to rifle.

Basically if you end up engaging enemies more often in long range then upgrading to sniper rifle would be a good thing, otherwise you may just stick with rifle.

According to the wiki page i've found here : http://sword-of-the-stars-the-pit.wikia.com/wiki/Weapons

            Dura    Mods    Acc Dmg Pen APM Mag Re  Rng
Rifle         50    3       45  10  70  1   8   3   ?   
Sniper Rifle  40    3       55  12  70  1   8   4   ?

So the durability of a sniper rifle is 10 less, but it does have 10 more accuracy and also it does 2 damage more. While the reload is 1 value less.