I personally like Gigalith more, because of its access to Stealth Rock via level up and bulk, but Excadrill does have better speed and Typing.
I much prefer Excadrill due to it's Speed, Sand Force Ability, Power, and wide array of moves. But Gigalith has an awesome advantage with it's superior Attack and Defense. And if it's under Sandstorm, it's Special Defense can be raised by 50%. Which can be a real problem and one heck of a powerful dual wall! o__o"
excadrill as a sweeper and gigalith as support pokmemon or as wall.
I must say excadrill looks cooler but who cares
My fc: 2108 6559 6304