When a car is lowered with lowering coils, the amount of travel between the top of the strut and the bumpstop is reduced. You can read suspension travel as ride quality. All lowering coil manufactures use coil design and spring rate to compensate for lost 'jounce' travel. Some drop coil sets instruct you to cut the bumpstops to create a bit more travel. Our drop coil Camaro clients are very pleased with the ride quality of our drop coils. I would hope they would be as we spend a lot of time getting the right balance between drop and ride quality.
Our coilovers are designed to maintain suspension travel, jounce travel regardless of ride height. We accomplish this with separate spring perch and ride height adjustment. In addition to suspension travel all our coilovers have adjustable damping. Between suspension travel and damping adjustment the ride quality is excellent.
Yu choice will depend on your expectations, use and driving style. The more miles you drive, the more aggressively you drive the more you will appreciate the benefits of coilovers. Ride height, suspension travel and damper maps are all elements of 5th Gen Suspension. We find that the lowest hanging fruit on a 5th Gen is not found in coils or coilovers, but rather in the sub-frame and radius bushes. To learn more about your 5th Gen suspension I suggest you set aside a bit of time and read
THE Book on 5th Gen Suspension available here on C5. With a good understanding of the how and why you'll be able to make an informed decision on where you'll spend you hard earned mod money first.