Actually you're just looking at a really new, inflationary token trying to find its market. The dex is by
definition more decentralized and so price discovery is spotty and volumes are generally low.
But for now, we are so diffuse and few that the centralized option is better.
I don't think decentralized vs centralized has any impact on price discovery or volume. The user interface should be close to identical between counterparty and melotic. I think It does have something to do with just current users/trading volume on the platform:
http://www.cryptoassetcharts.info/markets/info
Melotic: 24H - 13.15 BTC
Counterparty: 14H - 1.7BTC (I was manually adding up transaction values and got to 14hours worth and gave up)
NXT: 24H 38.63 BTC
Surprisingly the NXT Asset Exchange has more volume than counterparty and Melotic combined. I'm sure that will be a factor for other people looking to launch an Asset as it helps avoid the need or desire to also list on centralized exchanges.
I'm curious as to how blocktimes affect user adoption. Clearly trade execution times are dependant on this and users at some point may not like having to wait the long time for execution results. I wonder at what threshold and how much that affects whether users use the DEX or move assets into a centralized exchange for trading.