How much wheel gap do you want to eliminate? The Pro-Kit Spring Set will lower a vehicle generally 1.00" to 1.25", while the Sportline Spring Set will provide you with approximately 1.50" to 2.00" of lowering capabilities. To help you decide, check out "A Look at Lowering" to view the difference in ride height adjustments on various vehicles.
How important is ride quality to you? Lowering the car requires using higher spring rates to keep the car from bottoming out over bumps, but it comes at the cost of some ride smoothness.
Are you also looking to replace the dampers with aftermarket shocks and struts? If you want to re-use the Original Equipment dampers, you can do so with the Pro-Kit, although they may be a little soft for these springs (especially when worn) and may cause a bit of high-frequency undulation over severe bumps in the road, but it isn't a terrible sound. The Sportline kit is even lower and stiffer, so look into some new dampers with that kit, as well as an Eibach Recommended Alignment Kit to get your suspension geometry back into alignment. When you lower a car, the camber and caster can, and usually will change. It's important to get an alignment after installing either of these spring kits.
To see if these lowering springs are a good fit for your vehicle, visit our Upgrade Garage!