The Glyph Blackbox Plus portable drive is better than the G-tech G-Drive Mobile USB-C in nearly every way. While both drives support USB-C, allowing them to work with existing and future computers -- they will also work with Thunderbolt 3 ports by the way -- the Blackbox Plus has so much more to offer.
First of all, it supports USB 3.1 Gen 2 (10Gbps) as opposed to the Gen 1 (5Gbps) support of the G-Drive. Apart from the rugged aluminum casing, the Blackbox Plus has a removable protective rubber case to save it from accidental drops. It's also available in three hard drive-based capacities including 500GB, 1TB and 2TB priced at $100, $120 and $170, respectively; and two solid-state capacities including 512GB and 1TB that cost $230 and $450, respectively.
The G-Tech mobile drive, on the other hand, is available in a single hard drive-based capacity of 1TB for $120. What's more, the Blackbox Plus includes an interesting 3-2-1 warranty policy. You get 3 years of regular warranty against hardware failure, 2 years of free level-1 data recovery (meaning no advanced recovery method is required) and one year of advance replacement where if the drive is defective, Glyph will send the replacement right away before you have to send the defective drive back.
Most importantly, in testing, the Blackbox Plus did much better than the G-Drive. I tested the 1TB hard drive-based version through the USB 3.1 connection, using a USB-C cable with a USB-C computer and it scored a sustained real-word copy speed of 150MB/s for writing and 160MB/s for reading, among the highest for a portable drive of this type. This is likely because the drive houses a fast 7200-rpm internal drive on the inside. Note that the 2TB version of the Blackbox, however, houses a slower 5400-rpm internal drive, so its speed could be slower. On the other hand, the SSD-based version of the drive, which I haven't tested, will likely be much faster. The Blackbox is bus-powered, you won't need a separate power adapter, and it also works with USB 3.0 as as well as USB 2.0.
The Blackbox Plus includes pretty much every USB cable you'd ever need: two USB cables, one USB-A to USB-C cable and a USB-C to USB-C cable for computers with USB-C or Thunderbolt 3 port. The drive is quite compact, measuring just 3.7 inches by 5.75 inches at 0.8 inch thick, though it's still a bit bulkier than the G-Drive. Out of the box, the test drive was formatted in NTFS and works right away with a Windows computer but it can be easily reformatted to work with a Mac. Similar to the G-Drive, it doesn't support encryption to protect data against the case of loss or theft nor does it include any backup software. This is not a big deal, however, since in my experience, it's better to use Time Machine and Windows 10's built-in File History for backups anyway.
Should you get it?
If you're in the market for a fast, compact, rugged drive that will also work with future computers, you can't go wrong with the Blackbox Plus, of which I find the 1TB capacity to be the best deal. On the other hand if your computer doesn't have an USB-C (or Thunderbolt 3) port and you're not planning to upgrade anytime soon, a non-USB-C drive like the Seagate Backup Plus Ultra Slim or WD My Passport Ultra will offer lots of storage, albeit with slower performance, for about the same price.