redrick
First Post
This is ineffective past level 5. You can't reload either crossbow without a free hand; thus, you can't get your second attack from Extra Attack if you're using two crossbows. (Also, you have to have Crossbow Expert to even try it. The two-weapon fighting rules specify melee weapons.)
There really isn't a good way of dual wielding crossbows in 5E. The hand crossbow fighter build uses a single crossbow and takes advantage of a loophole in Crossbow Expert: A hand crossbow is a one-handed weapon, and Crossbow Expert doesn't specify that the hand crossbow has to be in addition to the one-handed weapon. They can be the same weapon! So you use a single hand crossbow for both the Attack action and the bonus action attack, leaving your other hand free to reload. This has the additional advantage that if you find a magic hand crossbow, you can use it for all your attacks.
A rogue could still benefit. This is similar to how a rogue uses two-weapon fighting. If you miss with your first attack, you can still get an off-hand attack and a chance to still get your sneak attack for the round. A hand-crossbow wielding rogue can get this without having to be in melee range. Could be particularly useful for Assassins, where there are extra bonuses specifically tied to the first round of combat.
A fighter or ranger wielding two hand crossbows could still drop the left hand crossbow and have a free hand to reload for extra attacks, I believe.
The difference between two-handed weapons and needing a hand to reload is that a two-handed weapon ties up both hands to be wielded, while loading a crossbow (especially with the crossbow expert feat) only needs that hand for a small amount of time. So a character with a free hand can use that free hand for other things, as long as they aren't holding or wielding something in that free hand. A character wielding a heavier crossbow needs both hands to effectively aim their weapon, so they couldn't use that free hand for things like casting spells. (If you choose to run it that way.)