To quote from another web page:
Modalert = Modafinil from Sun Pharma Modvigil = Modafinil from HAB Pharma
Waklert = Armodafinil from Sun Pharma Artvigil = Armodafinil from HAB Pharma
Modafinil = 50% R-Modafinil + 50% S-Modafinil Armodafinil = 100% R-Modafinil
S-Modafinil = short lasting R-Modafinil = long lasting
Modafinil consists 50/50 of the short lasting and the long lasting part. It usually comes in a dosage of 200mg. Armodafinil only consists of the long lasting part. It usually comes in a dosage of 150mg.
This means that in the beginning (first 5 hours), Modafinil might start off slightly stronger than Armodafinil, but won't last quite as long as Armodafinil. Armodafinil starts with a slightly weaker peak, but doesn't drop as much over the course of the day. Because of this, some people describe Armodafinil as being "smoother", while others prefer the (very slightly) "harsher" Modafinil.