It really depends on your use. If you plan to build a desktop replacement, thread performance matters. If you want a small cluster node for educational purposes, more slow cores are better.
That's great, but if you need crypto (because you have LUKS storage and send AES encrypted data over the network, like in a usual NAS case), A53 with aes instructions may be faster than this A72 without one. And so far it seems these cores don't have aes instructions.
Edit 2: Ah, also RPi3B and 3B+ didn't have those extensions. Oh well.
Edit 3: Just tested my bog standard RPi3B+ running Raspbian. It could do "openssl speed -elapsed aes-256-cbc" 43 MB/s AES-256-CBC. Tried also with "-multi 4" and it resulted 144 MB/s using all 4 cores. So perhaps RPi4 will be fast enough with CPU only crypto... would still love to have HW assist.
Edit 4: RPi4 running 32-bit OS can do about 65 MB/s per core aes-256-cbc. 85 MB/s per core for aes-128-cbc. So by using two CPU cores for encryption (+ heatsink + fan :-)) 1 Gbps ethernet can be saturated.
I believe it might be possible to use VideoCore VI for crypto acceleration.
I think it would be pretty tricky to get LUKS to use it, though. At least writing a kernel module, but most likely LUKS patch would be required. You'd probably have to choose between 3D acceleration and full disk encryption.
Looks like VideoCore VI is getting some compute shader support:
Yet, you can have the same priced board that can do 200-800MB/s AES-128 encryption (per core), leaving much more time to the actual useful work, or idle (less power consumption).
Quick Googling [0] revealed VideoCore VI might have at least some support for Vulkan and/or OpenCL. If this turns out to be true, then yes, VideoCore VI might be able to function as a crypto-coprocessor.
Depends on your use case. If you have SSD attached over USB3, you can easilly pull 400MB/s. This would severely limit that, if that is an encrypted drive. On Allwinner H6, for example, you could get that speed on oncrypted drive while still having other cores free for other stuff.
So if you need to go through/process gigabytes of data on encrypted drive, having to do encryption in SW will slow you down massively, especially if you also need to process the retrieved data somehow.
