I have half a dozen G-Drives, including the 1TB Thunderbolt drive, which I use as a Time Machine drive with my desktop.
I went with Samsung (first time ever!) because of the form factor of the T5. The G-Technology SSD is slightly cheaper, but it's very nearly the size of their 7200rpm HDDs.
I needed portability in this particular case, which made the T5 more appealing.
One other option is the SANDISK EXTREME 900. This looks super fast – almost 2x faster than the T5, but larger and heavier. I guess if you want ultimate portability go for the T5. For superfast performance and a little bigger, go for the 900...
Or look at Glyph's AtomRAID, much smaller than the Sandisk 900, faster as well.
http://www.idownloadblog.com/2017/09/20/glyph-atom-review-ssd-raid/
Other reviews has reported only 630MB/s performance rather than double the T5 (of 800MB/s)
Also the link above does not warn readers of the 200% risk of failure and data loss if one of the SSD's in the RAID fails..
The T5 is still a lot smaller and lighter (as well as compared to the smaller non RAID version)
630 MB/s hardly seems something to complain about, I saw that review and I think it’s the only one that had such low speeds, even after extended transfers.
I originally purchased the sandisk 900 and quickly noticed that transferring files over 4gb filled its cache and speeds dropped to sub 400MB/s. I also purchased t3 which has been great but it fell on my tile floor and the enclosure cracked, that was upsetting.
Ended up with 2x atom raids and have been super happy with them. Would probably crack my tile if dropped on it. Ssd’s have much higher mtbf than hdd’s. 200% percent of less than .1% is still a very small chance of failure. That said, I use them as video editing scratch disks and not long term backup.