Regarding the debate " Slings are simpler to use than crossbows" well...they are not indeed. There's a reason we dropped slings for crossbows and crossbows for guns.
Historically when crossbows were becoming more and more popular people seen them as " a weapon without honor". Cause you had a guy who since he was 6 learned how to wield a sword and shield, he devoted his entire life to be a guy in shiny armor. And then BUM, crossbows could pierce armor with ease. All you needed was a crossbow, a peasant, and a few days of training max.
You compare that to a sling and yeah, it's not easy to use at all. You need training to don't kill yourself with it and to aim properly. It got to a point where romans imported their slingers. A sling is a deadly weapon but if you want to kill a grown up men with it before he rushes at you with a javelin then you better be good at it. https://youtu.be/3uDtrwNY0Zk?t=234
Very interesting documentary btw, recommend watching it all ^^
Crossbows could not pierce armor with ease lol. Most Crossbows weren't much stronger than Longbows and also had much smaller projectiles. The reason why Crossbows became popularized was mainly because like you said they required less training to use, same with Muskets.
Bows in the Medieval period in particular weren't used like in Hollywood they were used at a fairly close range. Arrows lose a lot of power the longer they have to travel, so I imagine that a Longbow would still be '' better '' generally speaking because of the higher rate of fire and they weren't as clumsy to use in the middle of a battle. Which is why the English still used them and they were so feared because of the system the English had in place that essentially forced people to grow up to become Longbowmen. The reason why they were still effective even tho they couldn't pierce armor was quite simply because if you had thousands of arrows flying at you there was a high likelihood that some would hit a gap in your armor and against Cavalry kill your horse.
This is ofc speaking about plate armor. Most people wouldn't have that tho and I've seen arrows pierce shields and mail both and go into the arm holding the shield ( at a fairly close range, which again is why they were used at close range ). So yeah Longbows and Crossbows were incredibly effective at close range against pretty basic armor that most had, but definitely not against plate armor and it wasn't unique to Crossbows.
Edit: Same channel, video of Longbow vs a plate breastplate ( again, Longbows were about the same power Crossbows ).
