Really Oxy and H are just as different, or even less similar than Oxy and Hydro.
Oxy and Hydro are actually very similar structurally as far as I know, where as the two are very different from H when it comes to their molecular make up. H is a morphine derivative while both oxy and hydro are thebaine derivatives.
Methadone is not similar to any of those in any way other than the fact that it is a mu opiate agonist. Methadone has a structure and action that is very different from most opiates available making it very distinct.
Again like I said hydrocodone and oxycodone are very similar while Opana (oxymorphone), as far as I know is actually somewhat similar too. In fact Oxycodone is metabolized in the body into oxymorphone. Oxymorphone and Hydromorphone are the morphone derivitives of the codones hydrocodone and oxycodone.
As to your question about preference…well it is almost impossible for anyone to tell you what another person is going to like, but heroin and Methadone do have some very different feelings from those of hydro and oxy. H and done, in my opinion are going to be much more sedating while both hydro and oxy, especially oxy, have a somewhat stimulating effect to them.
Really though I/we can not tell you what someone is going to like better. I hate posts like this and I don’t even know why I even put this much time and effort into responding.