As elkhorn98 points out the Coast Redwood also known as Giant Redwood boasts that it is taller, the Giant Sequoia is slightly shorter but has more weight. A little information
(from Sequoia Kings Canyon Web Site) about the difference between the two trees.
Giant Redwoods
Live up to 2,000 years
Have branches up to 5 feet in diameter
Bark grows up to 12 inches thick
Can reproduce either by seed or by sprout
Giant Sequoias
Live up to 3,000 years
Have branches up to 8 feet in diameter
Bark grows up to 3 feet thick
Reproduce by seed only
Beyond just the difference in the trees however is the difference in their environment. Yosemite, Sequoia, and the coast all offer different experiences that go beyond just the trees. If you can manage it visiting all three areas is well worth it. At the very least consider visiting Yosemite along with the coast. If we get any snowfall it will be melting off by April and May. That is when the waterfalls in Yosemite are at their best.