Gauges
Wire gauge is a numerical system based on the diameter of a piece of wire. If braided wire is involved, the gauge number refers to the entire unit. This classification runs from 0 to 50, with zero being the largest (0.324 inches) and 50 the smallest (0.0010 inches). Wires thicker than 0.324 inches use a two-character system that ascends in numerical value as the wire diameter grows larger. For example, 2/0 gauge wire has a diameter of 0.348 inches and 4/0 gauge wire has a thickness of 0.400 inches.
Comparison
Therefore, 16 gauge wire is thicker than 19 gauge wire and so it is stronger, provided each sample of wire is made from the same material and is constructed in the same manner.
Considerations
Still the possibility exists that a strand of 19-gauge steel wire might be stronger than a larger piece of 16-gauge copper wire. The reason for this likelihood revolves around the numerous types of wire that are manufactured today and the various applications to which each kind of wire is used.