The benefits of having coilovers are that you can raise or lower the car at will, the downsides are more with cheap coilovers which can be very harsh and bouncy although all coilovers will make the ride less forgiving.
I've had coilovers on mine for 2 weeks now (mid price range ones) and to be honest i'm stil not sure they were worth it, the car looks great but it changes the character of the car from being good fun to push along on a-b roads to being hard work on anything but a smooth road as the coilovers make it skip and jump over bumps and ridges rather than soaking them up.
If you like to 'drive' your car then i would go for good quality shocks and lowering springs but if you want the looks and still some driveability then coilovers
