Totally agree. But a smaller, faster one is less predictable, so you can't bleed of small amounts of energy as easily / safely.
Which would you rather try to stop, with your bare hands, assuming identical energy? A 1-inch pipe spinning at 10,000 RPM, or a large tire spinning at 10?
One is more predictable than the other. In that video, I can point out when the arm will come around again with relative ease, and can very easily be accurate to below a tenth of a second.
Now picture it going several times faster in terms of RPM, and tell me when it'd be safe to stick your arm in its path.
Lets scale it up. Picture the earth. Near the equator, the linear velocity is almost 1000mph. Scale it down to the size of the centrifuge in the video, while keeping linear velocity the same. I can easily point out when half of the earth is facing the sun. Could you point out when the centrifuge is pointing north?
If you are planning to play chicken with a centrifuge, sure.
But I am more concerned with what happens if you do actually get hit. Or if it comes apart, or falls down.
And if you do get hit, or it breaks, a smaller faster one is MUCH (exponentially much) safer.
The force goes up by the RPM squared, but it goes down only linearly by radius. You don't need to speed it up very much to counteract the smaller size.
On the other hand the energy goes up by radius squared. Meaning the smaller size helps a LOT in terms of destructive power.
I've been too long out of physics, so I'll take your word on it. I wasn't sure how quickly size effected energy. Though I'll still take my chances with something I can predict if I have to interact with it.
One question though: is energy->radius^2 based on angular or linear velocity?
Which would you rather try to stop, with your bare hands, assuming identical energy? A 1-inch pipe spinning at 10,000 RPM, or a large tire spinning at 10?