USB Thumb drives have been faster that an SD card with my setup (mid-2011 iMac), but that will depend on the speed capabilities of the thumb drive and SD card you purchase. It also depends on the speed of the USB and SD ports on your Mac.
8GB is plenty big enough for the OS, but depending on how many apps you want to test and their requirements, you might need more.
On Wed, Oct 04, 2017 at 06:34 PM, Diane wrote:
> I want to create boot disk off a USB stick or SD card. I’d like to do some app testing on it if that’s possible. I know it would be slower than my current hard drive.
> Am I better of with one vs the other and what size should I get? I’ve done some searches and I’m saw 8gb for Sierra which sounds a bit low to me.