When my CD was recorded, I was stuck between Oasis CD and Discmakers. Was I going to duplicate or was I going to replicate?
Ultimately, I ended up going with oasiscd.com because, at the time, they were offering a CD promotional program. I think it's called their "Tools of Promotion." Basically, if you order so many CDs, you get free subscriptions to cdbaby.com, hostbaby.com (they host websites), sonicbids.com, some free display racks to help you sell your CD in local brick and mortar record stores and some other goodies that I can't remember. Basically, tools to help you push your CD so you come back for more. In addition, each one of those websites have their own goody packages that they offer. With cdbaby, for example, you get some limited digital distrubution which really helped me because I seem to be selling more downloads than CDs.
As for Discmakers, they were a little cheaper but they weren't offering anything in terms of CD promotion. At least, not at that time they weren't. I don't know about now. Maybe somebody else can speak up for Discmakers, I don't know much about them.
In the end, I guess you have to figure out what your needs are and who can provide you what you need at the most reasonable price. Don't always go for the cheapest. As cusebassman pointed out, there is a difference between duplication and replication make sure you know the difference.
I hope this helps you in your quest.