OC80 vs. Opana40 ER- which is preferred and why?

Hey guys- my pain doc wants to move me off of OC80 and into Opana 40 ER- everything I have read has me more curious then anything else.

The one thing I don't like about opana is that (from what I read) it shoots up your resistence- but other than that it seems that some like one or the other.

For those that have taken both- which do you prefer and why? As I said- just curious- the OC I have always liked but it effect is not what it once was