A coilover kit takes pressure off of the A arm and places it on the strut tower. This increases handling by decreasing suspension bind and unsprung weight, and is a fundamental setup for anyone looking to open track their car. If you get a quality kit, you will see an improvement in ride quality also.
Coilovers also allow very precise ride height adjustment...allowing you to dial in whatever height you want.
Yes the main benifit is weight, and reduced suspension bind. If you notice where your stock spring is (in the middle of the control arm). You will notice that the wheel rate is (the amount of the springs force acting at your wheel) is only about 50%. With a coil-over setup the spring is at the spindle so now your wheel rate is 90+%. So if you were to compare 600 in/lb springs (for coil-over vs. non coilover)the ride would be almost 2x as stiff with the coil overs since 540 in/lb of the spring force is acting on the wheel, where as only 300 in/lb of the force would be acting at the wheel in the stock setup. So where does the other half of the spring force from the stock setup go? Into your control arm bushings causing suspension bind, ride harshness, and more wear on the bushings (vs. a coil over setup). So there you go.....that's prolly more than you wanted to know .
Oh and thats just for the front. For the rear, the benifits are not nearly as much. In the back it just allows you to run lower arms w/o spring perches, adjust ride height, etc. THeres no real dynamic advantage as there is in the front. I suggest you get coil overs up front and may some LCA's w/ adjustable spring perches in the back.
Yes the main benifit is weight, and reduced suspension bind. If you notice where your stock spring is (in the middle of the control arm). You will notice that the wheel rate is (the amount of the springs force acting at your wheel) is only about 50%. With a coil-over setup the spring is at the spindle so now your wheel rate is 90+%. So if you were to compare 600 in/lb springs (for coil-over vs. non coilover)the ride would be almost 2x as stiff with the coil overs since 540 in/lb of the spring force is acting on the wheel, where as only 300 in/lb of the force would be acting at the wheel in the stock setup. So where does the other half of the spring force from the stock setup go? Into your control arm bushings causing suspension bind, ride harshness, and more wear on the bushings (vs. a coil over setup). So there you go.....that's prolly more than you wanted to know .