My experience has been good with WD portable drives (My Passport, WD Elements, WD Easystore, etc.). A total of 6 (so far) ranging in capacity from 1 TB to 4 TB have been used over the years for Time Machine and Carbon Copy Cloner backups for my household’s two iMac computers and for external storage (DVR function) for a Tablo TV antenna/DVR device.
You can find these on sale periodically at Best Buy, Amazon, etc. It’s useful to monitor websites such as 9to5Toys.com for sales and promotions. My last 4TB drive was $79, I think. You don’t need the Mac-specific products; just use the Mac’s Disk Utility app on the standard PC-compatible drives to erase/format to the MacOS Extended/Journaled format. Takes less than a minute. I pay no attention to WD or Seagate apps or encryption capabilities or backup apps - I don’t know how they work and don’t trust them.
Regarding the portable vs “desktop” drive versions: The portable drives are powered from the USB port. The “desktop” drives require connecting to a power outlet with the usual “wall wart”. This is inconvenient, in my view, and requires extra cable clutter. The portable drives are smaller and can be attached to the computer stand using velcro.
Caution: the USB cables provided with both the portable and low-cost desktop drives are thin and fragile. If you experience any problems, particularly involving intermittent connectivity, try using a substitute USB 3.0 cable to troubleshoot the problem. I experienced this problem once a few years ago, and WD promptly supplied a new cable. It’s probably a good idea to have one or two extra USB cables available “just in case”. Here is my recommendation:
Note that this cable is much larger (thicker) than the USB cables supplied with the WD or Seagate low-cost drives. Be very careful when handling and connecting/disconnecting your drives using the thin USB 3.0 cables.
Regarding SSD vs. HDD: I don’t see the point for using the faster SSDs for simple backup. The HDDs using USB 3.0 are fast enough, and the cost is much lower. The more expensive as faster SSDs are better used when the speed is really needed - fast access to media files for video editing, for example, or use as an external boot drive.
Time Machine and Carbon Copy Cloner apps work better when the external drive capacity is larger than the internal drive capacity. For my iMac’s 1TB internal SSD drive backup I use 2- or 4-TB external drives. This ensures adequate overhead capacity for “versioned” backups over extended periods of time. The 4TB drives tend to be the “sweet spot” these days for price/capacity value.
It’s difficult to assess reliability. Reviews on Amazon and elsewhere are generally good, but varied. Some swear by WD, some swear by Seagate. My experience has been fine, and I’m comfortable since there is additional online backup using Backblaze. Another strategy is to use multiple drives in a periodic rotation backup strategy. The drives are so inexpensive that they can be considered expendable - just use them (with a good backup strategy) while they work, then discard them. I tend to use each drive for a couple of years, then store it in a safe for a while as a “deep-background/archive” and replace it with a new drive (bought on sale, of course).
The tech-loving geek part of me really, really wanted to buy a NAS (Synology) to replace my multiple port-bale-drive strategy. That would have been fun (for a geek), but expensive and time-consuming to learn to use all of the capabilities. I finally decided to take my own advice: “Don’t make your life harder than it has to be”. If it works, and it’s simple, it’s good.