I have the dual-slot Sony reader, for no other reason than it was the one Hunt's had in stock the day I picked up the Z7. It wasn't worth ordering the less expensive model and paying shipping (it's under B+H's free shipping threshold) to save $30 before shipping.
It's certainly expensive for a card reader, but it seems well built. I've never used the SD slot, because the Thunderbolt 3 dock I have it plugged into has a fast SD slot of its own. The only reason to want that slot is if you don't already have a USB 3.0 (or faster) SD card reader, or if the one you have does nothing else and is taking up a USB port - use the Sony for both and save a port. If your SD slot is built into your computer, built into a hub or dock, or part of a USB 3.0 card reader you use for CF or another format, the SD slot is useless (if you have an older desktop or laptop with a built in SD reader, try the Sony to see if it's faster - some built in readers are actually USB 2.0).