Which muscle relaxer is stronger for back, neck, and leg spasms, from herniated discs, and sciatica, orphenadrine, or methocarbamol? thanks!

Depends on you and: whether other meds are considered. Zizatidine and cyclobenzaprine are better than the other two which are marginally beneficial!

It depends: Muscle relaxants work differently in different people. There's no clear "stronger/weaker". Sometimes methocarbamol helps while orphenadrine doesn't or vice versa. See what works for you.