One with metal arms is specifically an arbalast, which was the most powerful variant of handheld crossbow. Their power was absolutely higher than modern crossbows, by at least four times.
It doesn’t actually matter though. Most crossbows have far more power than bows, which make them stronger at short range, but their bolts all lose their power at a significantly faster rate.
As soon as the projectile leaves the string, it starts losing speed, and the mass of the projectile determines how quickly that happens. Arrows have higher mass and so lose their speed slower, giving them better range even when the draw weight is a fraction that of a crossbow, or especially an arbalest.
An arbalest had the power to punch a bolt through plate armor at close range, but warbows had twice the range of an arbalest.
They were used for castle defense not long range battle they only needed to penetrate armor hince the power they had. Even though they were handheld they were still a good defense
There were two types of archers in the medieval ages long range and short range long range archers had the regular bows and the short range archers had crossbows they were used both to defend the castle and first attack in battle sword and shield in the front line archers in the back