We do have both, and none is perfect.Cisco have more time on the market and more options.Also there is a ton. of information for free on the internet.
Quintum is not that complete, but getting better. The information is not so freely available,no much help unless you buy directly from Quintum.
Price of the equipment does not tell the whole story.Something could be cheap, but id you could not make it work, how much money will you loose????
If you go for Quintum, be sure to buy from a autorized dealer. Quintum will not give you support fro a second hand gateway from e-bay. At least not for free.
Whatever you do, do not go for Clarent, unless you enjoy pain and suffering.