If you drive hard or drive with enthusiasm or know your cars handling characteristics then you will notice straight away.
Don't buy from any online merchants just incase things go wrong so you have a physical shop to vent your problems.
copy's look just as good but if you strike a kerb or hit something there is a strong chance that it may split or shatter but originals mostly buckle.
i bought a combination of 2nd hand and new and refurbed them to look new but the final choice is yours.
its good for low looks & stance but if you don't do any spirited driving the handling is suspect.
in other words its rubbish. (I bought one by the way in 2012 from DPM performance).
I would conclude that you don't buy it.
save your dosh to buy better quality coilovers.