One of the big pluses to using an MRLS in renegade was that you could shoot around corners and arch the missiles. MRLS was always superior to an Artillery if the land wasn't flat (ex: hourglass hill) Big volley damages of MRLS was nice too for popping out and unloading and then hiding. I think the Artillery really shined in Renegade due to the map design. The maps were all small, pathways were small and small base entrances and seeing as the MRLS was more oriented toward ranged combat, it was inferior. Yeah, the Artillery has more range, but it's so inaccurate, you can barely hit anything but buildings at long ranges.
The Artillery did have more DPS that an MRLS though, and constant fire instead of having to reload for a few seconds.The MRLS missiles were a little too slow in Renegade. Made them very easy to evade if there was even the smallest obstacle nearby. Another problem with it was the homing mechanics in the game. Everything went toward the center of the model. Sitting behind an object or a slight raise in terrain elevation made it nearly impossible to hit Nod Light tanks on field since they were so short. One thing that really made a difference in the Artillery was it's mobility. It could turn 360 in less than a second, making it's slow moving turret a minor inconvenience.
Artillery body was long and solid too, making it easy to hide behind and repair. Mix that with it's agility, it was easy to block incoming vehicles and projectiles targeting the repairers. The MRLS has to point forward leaving little cover for a repairer. Not only that, but the MRLS isn't solid, long, or able to spin around at a whim. You can shoot between the missile pack and the "truck" to hit behind it. Artillery also had it's turret on it's very rear, allowing it to expose very little of itself when shooting around a corner. The MRLS could sort of do this to, but with the odd bugs in Renegade, missiles would often loop and hit the ground rather than going straight to the target if the MRLS was too close to a wall.