The Raspberry Pi doesn’t have a built-in interface for HD other than USB. Therefore the form factor of an SSD or any storage device is IMHO not that important.
If it’s solely on avoiden data loss of SD Cards - you should go for a device which offers that. SD Cards and SSDs (and USB Sticks) share some basic functionality:
So, if you’ll go on non-rotating HD (SSD) - have a look on the SLC (pricier!) ones - or use a bigger volume to decrease the chance of overwriting the same bit on the SSD over and over again.
I personally switched to an 5400rpm HD (yes, that good old fashioned HD), it’s 160GB and was 20 Bucks - together with a USB3 housing. (https://www.amazon.de/gp/product/B06WVCXQNS/).
There’s a guide here in the forum on how to “move root to SSD/USB”, and it works fine with the older Pis. The newer ones already have built-in boot-Option from USB (and PXE), which don’t even need an SD Card present:
PS: answer was accidentially posted here. Should have gone here: What kind of SSD for Raspberry Pi when using persistence? Sata, mSata or m.2?