If by Archer you mean Gilgamesh, then Enuma Elish (that functions the same way using his sword Ea) is stronger. But it doesn't by design use up most of his prana the way the Noble Phantasm Excalibur is meant to use most of Saber's. He is able to use it multiple times.
If you mean 5th War Archer...no. They don't even compare. UBW makes imitations only, they will always be weaker than the real thing.
If by "couple" you're including the one time against Gilgamesh right at the end, it wasn't the full power Excalibur. The only time she used it was the time she killed Rider. Her Noble Phantasm Excalibur is this.Hasn't she already used it a couple of times on the ground in the 5th war?
As I said, Excalibur the Noble Phantasm, not the sword itself, is extremely draining on her prana. They are two different things. The sword just happens to be her weapon of the same name and the tool used to unleash her Noble Phantasm. The Noble Phantasm is the sword's ability to convert her magical energy into light and accelerating it as a focused beam. She nearly faded away the first time she used it in the 5th War, that's how strong it is compared to her reserves. Since she has a much more competent mage as her Master in the 4th War, it should be less of a problem.