The first 2 swords Asta have are the demon slayer sword and the demon dweller sword. As far as I understand the demon dweller sword can nullify spells like the first sword, and it glows and it seems like it can fire some energy at long range when he makes a slash. How about the first sword? Does the first sword have any advantage over the second sword?
Here are the abililties of demon dweller sword:
• Anti magic
• Magic Absorption
• Ability to store magic from allies and fire it.
• Shoot anti magic slashes ( in the manga ).
And here are the abililties of demon slayer sword:
• Anti Magic
• Magic Deflection
• Ability to transform into black divider
• Ability to fly by manipulating anti magic flow ( in the manga ).
So, advantages are that it can deflect magic, reach a new destructive form, and can be used instead of a broom.
Hope this helps.