Eibach's are nice springs and are better than stock but are nowhere near the performance level of a good coilover. Kinda like a 240 is a nice sporty car, but its not a Ferrari!
For drifting I wouldn't even consider a set of springs. It's not to say some people dont drift on them, but they are nowhere as good as a set of cooilovers.
If you do go the spring route, then you will also need a good set of sway bars, front and rear to get the roll stiffness anywhere in the ballpark with a set of coilovers. By the time you spend $200 on a set of Eibachs and $300 on a set of sway bars, you are well on your way to a set of coilovers. I paid $680 for mine.