Have limited range of move in hip with discomfort. 1 dr says it is tight muscles, another chiropractor says need hip replace. which better mri or xray?

Both but...: start with the Xray - it would give you a good idea about moderate-severe arthritis (which would indicate a hip replacement), but more importantly for you it would give info about geometric parameters suggestive of FAI (femoral acetabular impingement). After that I might consider an MRI. Also check out this book on Amazon: "Heal Your Hips"