Depends what you use your car for.
It may compromise how much you can put in ur car with a 60mm drop for example.
And this forum likes cars
very low, personally i think 30mm drop looks fine, admittedly not as good as a 50 or 60 drop but it wont affect how u use ur car.
Anyway, its all up to you in end,
Make your car your own, how you want it!
Chris