For user using Prusa i3 (Merlin Firmware), better use Repetier Host. For Slicer, better use "Cura Engine". Fine build and stable print. Don't use "Slic3r". If you was a new born in 3D printing, Slic3r will be nightmare in printing. More setting must set and study and wasting our time to suit good setting for your prusa i3.
For new born user, I suggest using Repetier Host with Cura Engine setting.