Cost, durability, ease of use, and battery of life are some things that come to mind when comparing with your solution. Furthermore, I feel that to be as useful, the helicopter would have to implement autonomous or semi-autonomous control which is not trivial.
How do you make the helicopter rotors so that they don't break the first time they hit something and also don't cut people's faces up. In many situations, have a flying helicopter in a small space can be much more dangerous than a ball on the floor.
Sure, anything RC will be more complicated to use than a ball. But it's being marketed to professionals who will have been trained to use many tools.
The cost of RC helicopters is quite staggeringly low, and they are usually possible to repair. The blades can be painful if you fly into people, but I doubt people appreciate having balls land on them either. At least with an RC you could potentially see where you were heading and stop. If the use scenario is to send these in to places too dangerous to send people, I don't see much issue.
I don't think autonomous flying is necessary, but there has been research done to show it's possible (but as you say, not trivial).
I'm still unsure if a ball is going to work well, or whether it's just going to roll under a desk.
In most of their typical police/fire/first responder scenarios the users already have enough other things to do and track that they don't want to be trying to control an RC device as well.
It's also not advisable to assume that the users would be highly trained beforehand. A major benefit of a device like this is the fact that it is a very simple unit that is easy to deploy to get a quick and easy view of the environment around a corner or at the end of a tunnel.
Additionally in fires you have a lot of air drafts from the heat, making controlling an RC device even more challenging.
How do you make the helicopter rotors so that they don't break the first time they hit something and also don't cut people's faces up. In many situations, have a flying helicopter in a small space can be much more dangerous than a ball on the floor.