I would agree on Opana w/d being considerably harsher.
Personally I had very minor w/d issues with a daily Oxycodone habit.
When my source dried up & I was forced to switch to Oxymorphone it rapidly became a problem.
I used the intra-nasal route for my Oxymorphone, usually a nasal spray.
I found upon switching to Oxymorphone my tolerance skyrocketed quickly leading to a lack of euphoria without excessive doses.
I also found w/d's would hit me in a vastly shorter time frame with Oxymorphone than with Oxycodone.
Which I found odd considering Oxymorphone's longer half life.
Perhaps it was due to ROA as I took Oxycodone orally vs nasally for Oxymorphone but seeing as I was using IR Oxycodone it still seemed a little off.
As a matter of fact I ended up quitting cold turkey as I got so fed up with how quick & intensely w/d's would hit with Oxymorphone.
Also as BaybeX said Oxymorphone is a much more potent Opiate vs Oxycodone particularly if your using nasal admin.
IIRC Oxymorphone is 2x stronger than Oxcodone orally.
IIRC Oxymorphone has a 10% B/A orally vs 43% nasally.
Looking at those numbers 60mg of intra-nasal Oxymorphone is a whole fuck ton stronger than 60mg of Oxycodone orally.
Or if you were taking the Oxycodone nasally then it's an even bigger gap as oral Oxycodone has a higher B/A than nasal Oxycodone.
As such if you were doing intra-nasal Oxycodone then the jump to intra-nasal Oxymorphone is an even larger one.
So rather than weening down you instead drastically increased your opiate dependency / tolerance.
Anyways hope that information helps & a TLDR answer follows.
TLDR version; Basically I found Oxymorphone to have a lot more w/d related issues than I did with Oxycodone.