Unfortunately, the problem with opiate dependence is the high tolerance; lowering the tolerance causes the pain of withdrawal. Methadone binds to brain proteins and leaves the brain slowly, causing a longer, less intense withdrawal than oxycodone, which leaves the brain more quickly. But the total amount of misery eis the same either way-- shorter duration and more intense vs longer duration, a bit less intense.
The main issue though is not getting through withdrawal, but staying off opiates long term. In early addiction (i.e. the first few years of trying to quit) people tend to think 'if I could get through WD, I'd be OK'. Opiate addiction is usually a relapsing condition; after a few years many addicts get to a point where they are desperate enough to get through the withdrawal-- but they relapse at some point after they feel better. If you end up in that situation, do yourself the favor of seeking treatment sooner, rather than later.