In my experience
coilovers are much better, obviously they cost more money but, in my experience, i can take corners with much more control and stability with no understeer. Where as my friends that have springs cannot compete.
Problem is, your dampers are designed to be used with OEM springs at a certain height, you put
lower springs on and the damper will be compressed more than it would be, putting more strain on the damper and compromising handling.
I know
coilovers are more expensive, but the FK AK's i have were £195 free delivery from DPM are very good for a budget
coilover set.
Plus if you get adjustable ride height
coilovers then you can have it as low as you like, where as if you buy springs, it drops to a certain height and thats it, so if you dont like that height then you have to buy a new set!
If i was you, i would save up the extra £100 and get some JOM's from Damian (Similar to FK's but come with 2 years warranty)
And if you cant fit them yourself and dont wanna pay garage price then bring the car and
coilovers up to leeds and me and a mate will fit you for them.