A nylon guitar strap will allow the strap to move/shift on your clothing, while a leather/suede guitar strap will stick more to your clothing. It's a personal preference, really. There are a lot of nice (and inexpensive) straps out there. If the movement (or lack thereof) is your "problem", then maybe you could go to a guitar store and get a feel for the different straps available. Just a suggestion. Didn't quite understand your issue, though. Strap adjustment is important too. You need to find the adjustment that allows your strap/guitar to feel comfy and allow for full range of play. Experimenting with lengths is important.