The U.S. Trident SLBM (Sea Launched Ballistic Missile) set another record when it made its 126th successful test flight. No other strategic ballistic missile has been as reliable. The 58 ton, 44 foot long Trident II, has not had a test failure since 1989. The Trident had two failures during its 49 development test launches, but since then, it has been the most reliable SLBM to ever enter service. Each Trident II costs about $65 million and first entered service in 1990. Some of them are fired every year, to insure that the current configuration (of hardware and software) still works as it is supposed to. The Trident has a range of 11,000 kilometers.
In contrast, the latest Russian SLBM, the Bulava, is having an awful time in testing. While the overall (out of over 5,000 of them) failure rate for test launches of Russian rockets is eight percent (and the U.S. Trident I had a failure rate of 13 percent while in development), half of Bulava's development test launches have failed. The 48 ton, 56 foot long Bulava costs about the same as the Trident II. Such reliability is a crucial aspect of weapons, just like range and accuracy.
The 45 ton Bulava SCBM is a little shorter than the land based Topol M missile it is based on, so that it could fit into the missile tube on the submarine. Thus Bulava has a shorter range of some 8,000 kilometers. Bulava has three stages and uses solid fuel. Currently, each Bulava carries a single 500 kiloton nuclear weapon, plus decoys and the ability to maneuver. The warhead is also shielded to provide protection from the electronic pulse of nearby nuclear explosions. Take away all of these goodies, and the Bulava could be equipped with up to ten smaller (150 kiloton) warheads. But the big thing is still trying to defeat American anti-missile systems. But first Bulava has to get the bugs out. Russian SLBMs have long been plagued with development problems. Think of it as a tradition the Russians are still trying to lose.
It's always been assumed, by American military planners, that Russian ICBMs and SLBMs were less reliable. But even with that, enough of them would work, and kill millions of Americans, and cripple the economy for over a decade, if there were ever a nuclear attack.