There are several ways strollers could potentially be damaged when gate checking. Though gate checked items are loaded last, the baggage handlers aren't always the most careful with them. The items have to get from the end of the tunnel to the ground, loaded into the cargo hold, then taken out and brought back up to the tunnel at the arrival gate. Sometimes items are carried down manually and can be bumped or dropped, sometimes they are sent down a slide and again can be bumped or dropped. Sometimes they are physically thrown into the cargo hold by baggage handlers, which could cause damage, and oftentimes they will have other gate checked items thrown on top of them. They aren't tied down or anything in the cargo hold, so shifting of items can happen, and items can move around, fall over, etc, further causing damage. Also, if the baggage handlers can't figure out how to collapse a stroller, they could damage it trying to do so, or will just throw it in the cargo hold not collapsed. Then, if other stuff is thrown on it or it shifts during flight, there's a great potential for damage. The clips that hold a stroller closed can break easily, also attachments like the canopy or cup holders can break off if other strollers or heavy gate checked items are placed on them and they move around during flight. Items can easily get scratched or dirty moving around in the cargo hold, or wet if it's raining while they are loading or unloading.
Having said that, we have never sustained damage to our gate checked stroller, but it can and does happen. DH works for an airline (though not as a baggage handler), and personally sees how gate checked items are often handled. I don't think it's so much a one airline is better than another issue but an issue of some baggage handlers being more careful than others, as well as things outside anyone's control, like items shifting during flight, etc. That's also why it's so hard to claim damage. It's difficult to prove that it was done by negligence/rough handling by employees, vs damage sustained through items moving in the cargo hold.
