Not necessarily true. In fact given solid state hardware limited times it can be written to, I'm more inclined to trust hard drives for important back ups.
They're also safer when it comes to recovering data when things go bad.
With solid state there's the risk of corrupt media meaning data is gone for good. With magnetic media there's more you can do should things go bad.
There's also the fact that controllers are limiting speed on the Amiga, so there's little performance to gain.
Well, I disagree. For two main reasons. First, you can write protect an SD card. Second, SD cards do not have issues with local magnetic fields, or earthquakes, which is kind of of an issue if you live in certain parts of the world like Sacramento.
It's true that SD cards won't work to full speed connected to most Amigas, and the actual speed you can get get is throttled badly with some SCSI stuff because it's limited to asynchronous mode. To about 2.5 MB/S.
You can get maybe 16 and some out of some arrangements on IDE, and I think the ceiling is about 20 MB/S. Maybe some ultra fast and wide arrangements can go faster again, but I think there's a limit to the throughput of any sort of native Amiga interface. More so on GVP, maybe, but it's not the worst either. I've no idea what the OP's machine is really like, from the post anyway.
How well the Amiga controller handles solid-state storage is an issue. That's true.