Which is better for pain.....diclofenac potassium 50mg or ibuprofen 600mg?

Both are excellent: anti-inflammatory. I personally think that if you had to make a choice, diclofenac, may be a speck stronger, but not that much more than ibuprofen. Both can be irritating to the stomach and cause systemic issues on the long term

Depends: Ibuprofen, since it's over the counter, is usually tried by people before they make their way to the doctor, and is effective for many people. If ibuprofen "doesn't pack enough punch" then the doctor might prescribe them diclofenac potassium, which is stronger.