Usually people do what's known as "tensile testing" to compare the tensile strength of various materials. Typically, identically sized and shaped samples of the materials are prepared and individually placed in a machine that pulls,,in a controlled manner, on the materials in one direction. Materials with higher tensile strength will be able to be stretched or pulled to a greater extent before failing or breaking than materials with lower tensile strength.

Since you probably don't have such a machine at home, one thing you could try is clamping the material down at one end at a fixed position. At the other end, pull the material slowly and consistently until it breaks. Measure how far you were able to pull it before it broke. Do this several times for each material in question, as consistently as possible, and then average the data. I hope this helps!

You do an experiment! You take a set length and width of each, and then attach heavier and heavier weights to them until they break or otherwise fail.