Security is much better with a rubber/nylon/leather band. You only have to worry about the two pins, but in the case of a steel bracelet, you have a lot of "potential failures" with all these links.
Although a top quality steel bracelet should be well made and dependable, I have seen such a failure. It only happened once in my lifetime, but once is enough for me to feel uneasy about holding my hand outside the boat when powerboating or jet-skiing.
For top security, choose one of the nylon watchbands that are threaded through the pins and passing under the watch. Even if one of the pins fails, the watch is held on your wrist by the other pin.